U.S. patent application number 14/974399 was filed with the patent office on 2016-04-21 for vapor deposition of metal oxides, silicates and phosphates, and silicon dioxide.
The applicant listed for this patent is President and Fellows of Harvard College. Invention is credited to Jill S. BECKER, Roy Gerald GORDON, Dennis HAUSMANN, Seigi SUH.
Application Number | 20160111276 14/974399 |
Document ID | / |
Family ID | 26929629 |
Filed Date | 2016-04-21 |
United States Patent
Application |
20160111276 |
Kind Code |
A1 |
GORDON; Roy Gerald ; et
al. |
April 21, 2016 |
VAPOR DEPOSITION OF METAL OXIDES, SILICATES AND PHOSPHATES, AND
SILICON DIOXIDE
Abstract
Metal silicates or phosphates are deposited on a heated
substrate by the reaction of vapors of alkoxysilanols or
alkylphosphates along with reactive metal amides, alkyls or
alkoxides. For example, vapors of tris(tert-butoxy)silanol react
with vapors of tetrakis(ethylmethylamido)hafnium to deposit hafnium
silicate on surfaces heated to 300.degree. C. The product film has
a very uniform stoichiometry throughout the reactor. Similarly,
vapors of diisopropylphosphate react with vapors of lithium
bis(ethyldimethylsilyl)amide to deposit lithium phosphate films on
substrates heated to 250.degree. C. Supplying the vapors in
alternating pulses produces these same compositions with a very
uniform distribution of thickness and excellent step coverage.
Inventors: |
GORDON; Roy Gerald;
(Cambridge, MA) ; BECKER; Jill S.; (Cambridge,
MA) ; HAUSMANN; Dennis; (Los Gatos, CA) ; SUH;
Seigi; (Cary, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
President and Fellows of Harvard College |
Cambridge |
MA |
US |
|
|
Family ID: |
26929629 |
Appl. No.: |
14/974399 |
Filed: |
December 18, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14959283 |
Dec 4, 2015 |
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14974399 |
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14587909 |
Dec 31, 2014 |
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14959283 |
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13719110 |
Dec 18, 2012 |
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14587909 |
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12407556 |
Mar 19, 2009 |
8334016 |
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13719110 |
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11199032 |
Aug 8, 2005 |
7507848 |
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12407556 |
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10381628 |
Sep 2, 2003 |
6969539 |
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PCT/US01/30507 |
Sep 28, 2001 |
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11199032 |
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60253917 |
Nov 29, 2000 |
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60236283 |
Sep 28, 2000 |
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Current U.S.
Class: |
257/410 ;
257/532; 438/785 |
Current CPC
Class: |
H01L 29/0684 20130101;
H01L 29/517 20130101; C01B 13/34 20130101; C23C 16/401 20130101;
H01L 21/02271 20130101; H01L 29/42364 20130101; H01L 21/31612
20130101; H01L 28/40 20130101; C23C 16/40 20130101; H01L 21/02148
20130101; C01B 25/30 20130101; C01G 27/02 20130101; C07F 9/091
20130101; H01L 21/0228 20130101; C23C 16/45531 20130101; H01L
21/02164 20130101; C23C 16/405 20130101; C23C 16/30 20130101; C01B
25/36 20130101; C01G 35/00 20130101; H01L 21/02156 20130101; C07F
9/11 20130101; H01L 21/02159 20130101; C01G 25/02 20130101; C23C
16/45525 20130101; H01L 21/02112 20130101; C23C 16/402 20130101;
C23C 16/45553 20130101; H01L 21/3141 20130101; C23C 16/455
20130101; H01L 21/02205 20130101; C01B 33/26 20130101; C01B 33/126
20130101; C01B 33/20 20130101; H01L 21/02178 20130101 |
International
Class: |
H01L 21/02 20060101
H01L021/02; H01L 49/02 20060101 H01L049/02; H01L 29/51 20060101
H01L029/51 |
Goverment Interests
STATEMENT AS TO FEDERALLY SPONSORED RESEARCH
[0002] This invention was made with the support of the United
States government under National Science Foundation Grant No.
ECS-9975504. The United States has certain rights in the invention.
Claims
1. A microelectronic device comprising: an insulating metal oxide
layer; wherein the insulating metal oxide layer is prepared by a
process comprising: exposing a substrate alternately to a vapor of
a first reactant component and a vapor of a second reactant
component; wherein deposition of the first reactant component and
the second reactant component are self-limiting; wherein said first
reactant component comprises a metal alkylamide; wherein said
second reactant component interacts with the deposited first
reactant component to form the insulating metal oxide layer; and
wherein said insulating metal oxide layer comprises oxygen and the
metal from the metal alkylamide.
2. The microelectronic device of claim 1, wherein the insulating
metal oxide layer insulates a gate or capacitor.
3. The microelectronic device of claim 2, wherein the metal
alkylamide is a hafnium dialkylamide.
4. The microelectronic device of claim 3, wherein the hafnium
dialkylamide is tetrakis(ethylmethylamido)hafnium.
5. The microelectronic device of claim 3, wherein the hafnium
dialkylamide is tetrakis(dimethylamido)hafnium.
6. The microelectronic device of claim 3, wherein the hafnium
dialkylamide is tetrakis(diethylamido)hafnium.
7. The microelectronic device of claim 2, wherein the metal
alkylamide is a zirconium dialkylamide.
8. The microelectronic device of claim 7, wherein the zirconium
dialkylamide is tetrakis(ethylmethylamido)zirconium.
9. The microelectronic device of claim 7, wherein the zirconium
dialkylamide is tetrakis(dimethylamido)zirconium.
10. The microelectronic device of claim 7, wherein the zirconium
dialkylamide is tetrakis(diethylamido)zirconium.
11. The microelectronic device of claim 1, wherein the substrate
has a hole and the insulating metal oxide layer conformally coats
said hole.
12. The microelectronic device of claim 11, wherein the hole has a
length to diameter ratio of greater than 40.
13. The microelectronic device of claim 11, wherein the hole
comprises a trench.
14. The microelectronic device of claim 11, wherein the substrate
comprises silicon.
15. The microelectronic device of claim 11, wherein the insulating
metal oxide layer has a thickness that varies by less than 1%.
16. A microelectronic device comprising: an insulating metal oxide
layer; wherein the insulating metal oxide layer is prepared by a
process comprising: introducing a vapor of a first reactant
component into a deposition chamber; introducing a vapor of a
second reactant component into the deposition chamber; alternately
repeating the introduction of the first reactant component and the
second reactant component; wherein deposition of the first reactant
component and the second reactant component are self-limiting;
wherein said first reactant component comprises a metal alkylamide;
wherein said second reactant component interacts with the deposited
first reactant component to form the insulating metal oxide layer;
and wherein said insulating metal oxide layer comprises oxygen and
the metal from the metal alkylamide.
17. The microelectronic device of claim 16, wherein the insulating
metal oxide layer insulates a gate or capacitor.
18. The microelectronic device of claim 17, wherein the metal
alkylamide is a hafnium dialkylamide.
19. The microelectronic device of claim 18, wherein the hafnium
dialkylamide is tetrakis(ethylmethylamido)hafnium.
20. The microelectronic device of claim 18, wherein the hafnium
dialkylamide is tetrakis(dimethylamido)hafnium.
21. The microelectronic device of claim 18, wherein the hafnium
dialkylamide is tetrakis(diethylamido)hafnium.
22. The microelectronic device of claim 17, wherein the metal
alkylamide is a zirconium dialkylamide.
23. The microelectronic device of claim 22, wherein the zirconium
dialkylamide is tetrakis(ethylmethylamido)zirconium.
24. The microelectronic device of claim 22, wherein the zirconium
dialkylamide is tetrakis(dimethylamido)zirconium.
25. The microelectronic device of claim 22, wherein the zirconium
dialkylamide is tetrakis(diethylamido)zirconium.
26. The microelectronic device of claim 16, wherein the substrate
has a hole and the insulating metal oxide layer conformally coats
said hole.
27. The microelectronic device of claim 26, wherein the hole has a
length to diameter ratio of greater than 40.
28. The microelectronic device of claim 26, wherein the hole
comprises a trench.
29. The microelectronic device of claim 26, wherein the substrate
comprises silicon.
30. The microelectronic device of claim 26, wherein the insulating
metal oxide layer has a thickness that varies by less than 1%.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/959,283, filed on Dec. 4, 2015, which is a
continuation of U.S. patent application Ser. No. 14/587,909, filed
on Dec. 31, 2014, which is a continuation of U.S. patent
application Ser. No. 13/719,110, filed on Dec. 18, 2012, which
claims the benefit of the filing date of U.S. patent application
Ser. No. 12/407,556, filed on Mar. 19, 2009, now U.S. Pat. No.
8,334,016, which claims the benefit of the filing date of U.S.
patent application Ser. No. 11/199,032, filed on Aug. 8, 2005, now
U.S. Pat. No. 7,507,848, which claims the benefit of the filing
date of U.S. patent application Ser. No. 10/381,628, filed on Sep.
2, 2003, now U.S. Pat. No. 6,969,539, which is the national stage
application of PCT Application No. US01/30507, filed on Sep. 28,
2001, which claims the benefit of the filing date of U.S.
Provisional Patent Application Nos. 60/236,283, filed Sep. 28, 2000
and 60/253,917, filed Nov. 29, 2000, the contents of which are
hereby incorporated by reference herein in their entireties.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to novel reagents for use in thin
film deposition processes such as chemical vapor deposition (CVD)
and atomic layer deposition (ALD). These reagents can be used for
deposition of materials containing silicon and/or phosphorus along
with metals and/or oxygen, commonly called metal oxides, silicates
or metal phosphates, or silicon dioxide.
[0005] 2. Description of the Related Art
[0006] Chemical vapor deposition (CVD) is a widely-used process for
forming solid materials, such as coatings or powders, from
reactants in the vapor phase. Comprehensive reviews of CVD
processes have been given recently in CVD of Nonmetals, W. S. Rees,
Jr., Editor, VCH Publishers, Weinheim, Germany, 1996; CVD of
Compound Semiconductors, A. C. Jones and P. O'Brien, VCH, 1996; and
The Chemistry of Metal CVD, T. Kodas and M. Hampden-Smith, Editors,
VCH, 1994.
[0007] In CVD processes, a reactant vapor or vapor mixture is
brought into contact with a heated surface on which a thin film is
deposited. In a related form of CVD, two reactant vapors are
alternately exposed to the heated surface. This form of CVD is
often called atomic layer deposition (ALD). For suitable reactants,
ALD can provide improved step coverage and thickness uniformity
compared to CVD with mixed vapors. For a review of ALD, see the
paper by Mikko Ritala in Applied Surface Science, volume 112, pages
223-230 (1997).
[0008] Coatings of metal silicates have many applications or
potential applications. For example, silicates of zirconium,
hafnium, yttrium or lanthanum are being considered as potential
replacements for silicon dioxide in gate insulators in silicon
semiconductor technology. See, for example, A. Kingon et al.,
Nature, volume 406, pages 1032-1038 (2000). In Science, (volume
288, pages 319 to 321 (2000)), Ritala et al. report the use of the
sequential ALD reaction of metal chlorides and silicon alkoxides to
produce metal silicates, including zirconium silicate. However,
this reaction deposits films containing residual chlorine, which
can be deleterious to the properties of the film or to its adhesion
to substrates or subsequent coatings. The chlorine in the
precursors can also corrode metal substrates or the apparatus used
for the deposition. Thus it would be advantageous to have
chlorine-free precursors for CVD or ALD of metal silicates or
oxides.
[0009] ALD of silicon dioxide has been achieved by Klaus et al.,
U.S. Pat. No. 6,090,442 (2000), but the deposition rate is very
slow and the substrate temperature is limited to values near room
temperature.
[0010] Lithium phosphate is a material of current interest as a
lithium ion conductor in lithium batteries. Currently there is no
known process for CVD or ALD of lithium phosphate.
SUMMARY OF THE INVENTION
[0011] A principal feature of the present invention includes
volatile chemical precursors with reactivity adapted for CVD or ALD
of metal silicates, phosphates or oxides.
[0012] An advantage of these chemical precursors is that they do
not contain chlorine, and leave no chlorine residue during a
process for the CVD or ALD of metal silicates, phosphates or
oxides.
[0013] A related feature of the present invention is the deposition
of metal silicates under conditions that produce a sharp interface
between silicon substrates and the deposited metal silicate.
[0014] An advantage of the process is that it permits deposition of
materials containing metal silicates or phosphates by a CVD process
in which all the reactants may be mixed homogeneously before
delivery to the heated surface of the substrate.
[0015] An additional advantage of the process is the vapor
deposition of metal silicates or phosphates with relatively fixed
ratio of metal to silicon over a range of conditions such as
concentrations of reactants and position of the substrate inside
the reactor.
[0016] Another advantage of the invention is its ability to make
conformal coatings over substrates with narrow holes, trenches or
other structures. This ability is commonly known as good step
coverage.
[0017] Another feature of the present invention is the preparation
of material comprising lithium phosphate.
[0018] An advantage of the invention is that the reactants are
stable and relatively nonhazardous.
[0019] Another feature of the invention includes a chemical vapor
deposition or atomic layer deposition process for metal oxides or
mixtures of metal oxides.
[0020] A further feature of the invention includes process for
atomic layer deposition of silicon dioxide.
[0021] One particular feature of the present invention includes a
process for depositing oxides or silicates of zirconium, hafnium,
yttrium and/or lanthanum having high dielectric constants of use as
gate insulators or trench capacitors in microelectronic
devices.
[0022] Another particular feature of the present invention includes
a process for depositing silicon dioxide or metal silicates having
useful optical properties, such as in planar waveguides and
multiplexers/demultiplexers, and in optical interference
filters.
[0023] An additional feature of the present invention includes a
process for depositing lithium phosphate coatings allowing rapid
diffusion of lithium for use as separators in batteries or
electrochromic devices.
[0024] Other features and advantages of the invention will be
obvious to those skilled in the art on reading the instant
invention.
[0025] In one aspect of the invention vapors of alkoxysilanols are
reacted with the vapors of suitably reactive metal or metalloid
compounds, such as metal or metalloid alkylamides, alkyls or
cyclopentadienyls, to form metal silicates. The reaction may be
carried out in a manner to form films.
[0026] In at least some embodiments, tris(alkoxy)silanol compounds
have the general formula 1, in which R.sup.n represents hydrogen,
alkyl groups, fluoroalkyl groups or alkyl groups substituted with
other atoms or groups, preferably selected to enhance the
volatility of the compound, where R.sup.n is any one of R.sup.1
through R.sup.n. The R.sup.n may be the same or different from each
other.
##STR00001##
[0027] In at least some embodiments methyl groups are selected for
each of the R.sup.n in the general formula 1 given above one
obtains a highly preferred compound tris(tert-butoxy)silanol 2,
which may be written more compactly as (.sup.tBuO).sub.3SiOH.
##STR00002##
[0028] Another compound of the invention is
tris(tert-pentyloxy)silanol, also known as
tris(tert-amyloxy)silanol 3, which may be written more compactly as
(.sup.tAmO).sub.3SiOH.
##STR00003##
[0029] In at least some embodiments of the invention
Di(alkoxy)silanediols such as (.sup.4BuO).sub.2Si(OH).sub.2 can
also be used, although they are less stable than
tris(alkoxy)silanol compounds in at least some applications.
Di(alkoxy)silanediol compounds having the general formula 4 may be
used according to the invention, where R.sup.n, represents
hydrogen, alkyl groups, fluoroalkyl groups or alkyl groups
substituted by other atoms or groups, preferably selected to
enhance volatility and stability, and may be the same or different
for any R.sup.n, and R.sup.n is any of R.sup.1 through R.sup.6 may
be the same or different.
##STR00004##
[0030] In at least some embodiments, the groups R.sub.1 for the
general formula 1 or R.sup.1-R.sup.6 for the general formula 4 may
be selected from the group consisting of hydrogen, methyl, ethyl,
n-propyl and isopropyl groups.
[0031] In the foregoing compounds, it is also understood that the
alkyl groups R.sup.1 through R.sup.9 for general formula or R.sup.1
through R.sup.6 for general formula 4 may be a hydrocarbon having
some degrees of unsaturation, e.g., aryl, alkenyl or alkynyl
groups.
[0032] In at least some embodiments, metal compounds include those
that react readily with the slightly acidic protons in silanols.
These acidic protons are the ones attached directly to oxygen in
the silanol. Metal compounds that generally react with these acidic
protons include most metal alkyls and other organometallic
compounds, metal alkylamides, and some metal alkoxides. The
reactivity of any particular compound can be established readily by
mixing it with an alkoxysilanol and analyzing the mixture for
products by techniques such as nuclear magnetic resonance (NMR). We
have found that compounds that are known to react with water also
generally react with alkoxysilanols.
[0033] We have also discovered that the stoichiometry of the
deposited metal silicates can be controlled. The silicon/metal
ratio may be decreased by replacing some or all of the silanol with
water or an alcohol. Conversely, the silicon/metal ratio may be
increased by replacing some or all of the metal source by a
suitably reactive silicon-containing compound such as a silicon
amide or a silylene. By these methods the composition of the
deposited material may be chosen to be any composition from pure
metal oxide to pure silicon dioxide or any desired silicon/metal
ratio in between. The stoichiometry may even be varied during the
course of one deposition. For example, in the deposition of a gate
insulator for a silicon semiconductor device, it may be desirable
to begin the deposition with a silicon-rich layer close to the
silicon surface in order to improve the electrical properties of
the interface, followed by a metal-rich layer with higher
dielectric constant.
[0034] In another aspect of the invention, vapors of
bis(alkyl)phosphates are reacted with the vapors of reactive metal
compounds, such as metal alkylamides, metal alkyls, metal
cyclopentadienides or metal alkoxides, to form metal phosphates.
The reaction may be carried out in a way that forms films.
[0035] In at least some embodiments of the invention,
phosphorus-containing precursors include bis(alkyl)phosphates 5 in
which R.sup.n, represents hydrogen, alkyl groups, fluoroalkyl
groups or alkyl groups, substituted with other atoms or groups
where R.sup.n may be any of R.sup.1 through R.sup.6. The R.sup.n
may be the same or different from each other.
##STR00005##
[0036] In at least one embodiment, the phosphorus precursor is
diisopropylphosphate, represented by the formula 6.
##STR00006##
[0037] It is also possible to control the stoichiometry of the
metal phosphates. The phosphorus/metal ratio may be decreased by
replacing some or all of the bis(alkyl)phosphate with water or an
alcohol. Conversely, the phosphorus/metal ratio may be increased by
replacing some or all of the metal source by a suitably reactive
phosphorus source. By these methods, the composition of the
deposited material may be varied from pure metal oxide to pure
phosphorus oxide or any desired phosphorus/metal ratio.
[0038] In at least some embodiments, the groups R--R.sup.6 for the
general formula 5 may be selected from the group consisting of
hydrogen, methyl, ethyl, n-propyl or isopropyl groups. In the
foregoing compounds, it is also understood that the alkyl groups
R.sup.1 through R.sup.9 for general formula 1 or R.sup.1 through
R.sup.6 for general formula 4 may be a hydrocarbon having some
degrees of unsaturation, e.g., aryl, alkenyl-alkynyl groups.
[0039] In another aspect of the invention, a process for preparing
a material comprising silicon includes exposing a substrate to one
or more vapors chosen from the group consisting of alkoxysilanols,
alkoxysilanediols and silylenes. In at least some embodiments, the
silylene is the compound described by the formula
##STR00007##
where R is an alkyl group, or R is tert-butyl.
[0040] In one aspect of the invention, a process for forming a
material including phosphorus includes exposing a substrate to one
or more vapors chosen from the group consisting of
bis(alkyl)phosphates, phosphorus(III) oxide and white
phosphorus.
[0041] In another aspect of the invention, a process is provided
for preparing oxygen-containing materials including exposing a
substrate to one or more vapors chosen from the group consisting of
arene hydrates, such as benzene hydrate, naphthalene hydrate, or a
substituted benzene hydrate or a substituted naphthalene
hydrate.
[0042] In another aspect of the invention, a process for forming a
metal oxide is provided including exposing a heated surface
alternately to the vapor of one or more metal amides and then to
the vapors of water or an alcohol.
[0043] In at least some embodiments, the alcohol is an arene
hydrate, or in at least some embodiments, the metal amide or amides
are chosen from Table 1.
[0044] In another aspect of the invention, a process for forming
material including oxygen and one or more metals is provided by
exposing a surface alternately to the vapor of one or more
organometallic compounds and to the vapor of an arene hydrate.
[0045] In at least one embodiment, the organometallic compounds are
chosen from Table 2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] Various objects, features, and advantages of the present
invention can be more fully appreciated with reference to the
following detailed description of the invention when considered in
connection with the following drawings. The drawings are presented
for the purpose of illustration only are not intended to be
limiting of the invention, in which:
[0047] FIG. 1 is a cross-sectional illustration of an atomic
deposition layer apparatus used in the practice of at least one
embodiment of the invention;
[0048] FIG. 2 is a cross-sectional illustration of an atomic
deposition layer apparatus used in the practice of at least one
embodiment of the invention; and
[0049] FIG. 3 is a cross-sectional scanning electron micrograph of
holes in a silicon wafer uniformly coated with hafnium dioxide
using one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
1. Metal Silicates and Silicon Dioxide
[0050] The present invention provides a method for preparing metal
silicates of varying metal and silicon content. The method involves
the reaction of a vapor of an alkoxysilanol or alkoxysilanediol
with a vapor of one or more metal or metalloid compounds. The
compound may be formed as a powder or as a film on a substrate, and
in some embodiments, on a heated substrate. The compound may be
formed on a substrate by mixing the vapors of the alkoxysilanol or
alkoxysilanediol and the metal or metalloid compound prior to
deposition on a substrate. In at least some embodiments, a
substrate is alternately exposed to a alkoxysilanol or
alkoxysilanediol vapor and a vapor of one or more of a metal or
metalloid compound.
[0051] Silanol and silanediol reactants are commercially available
or may be prepared using conventional or known techniques. Silicon
precursor, tris(tert-butoxy)silanol, is commercially available from
Aldrich Chemical Company (Milwaukee, Wis.) and Gelest, Inc.
(Tullytown, Pa.). Tris(tert-butoxy)silanol may be prepared as
follows. First tris(tert-butoxy)chlorosilane is made by either of
the following two reactions:
SiCL.sub.4+3.sup.tBuOH.fwdarw.(.sup.tBuO).sub.3SiCl+3HCl (1)
SiCl.sub.4+3NaO.sup.tBu.fwdarw.(.sup.tBuO).sub.3SiCl+3NaCl (2)
The tris(tert-butoxy)chlorosilane is then hydrolyzed according to
the reaction
(.sup.tBuO).sub.3SiCl+H.sub.20.fwdarw.(.sup.tBuO).sub.3SiOH+HCl
(3)
[0052] See, Backer et al, Rec. Trav. Chim., volume 61, page 500
(1942). This compound is a solid at room temperature and melts at
about 66.degree. C. It sublimes at room temperature at a low
pressure of about 10.sup.-4 Torr, and can be distilled at a
temperature of about 104.degree. C. at a pressure of 20 Torr. It is
highly soluble in organic solvents such as mesitylene or
tetradecane, so that its vapors can be formed conveniently by flash
vaporization of its solution.
[0053] Other tris(tert-alkoxy)silanols may be prepared by similar
reactions, by substituting other tertiary alcohols, such as
ferr-pentyl alcohol (also known as tert-amyl alcohol), for
tert-butanol. Tris(tert-amyloxy)silanol, (.sup.tAmO).sub.3SiOH, is
a liquid at room temperature, so its vapors can be formed
conveniently by flash vaporization of the neat liquid. It has a
vapor pressure of about 2 Torr at 96.degree. C. It is commercially
available from Aldrich Chemical Company.
[0054] Silanols and silanediols may be reacted with a metal source
to obtain a metal silicate. The metal source may contain one or
more metals and the resultant metal silicate may contain one or
more metals. In at least some embodiments, metal compounds include
those that react readily with the slightly acidic protons in
silanols. These acidic protons are the ones attached directly to
oxygen in the silanol. Metal compounds that generally react with
these acidic protons include most metal alkyls and other
organometallic compounds, metal alkylamides, and some metal
alkoxides. The reactivity of any particular compound can be
established readily by mixing it with an alkoxysilanol and
analyzing the mixture for products by techniques such as nuclear
magnetic resonance (NMR). We have found that compounds that are
known to react with water also generally react with
alkoxysilanols.
[0055] The reaction is carried out in the vapor state and may be
carried out using CVD or ALD techniques. As is discussed in greater
detail below, ALD provides control over the deposition process and
is suitable for use in a wide range of reaction conditions and
reactant reactivity.
[0056] The silicon/metal ratio may be increased by replacing some
or all of the metal precursor by a suitably reactive silicon
compound. Silicon halides such as silicon tetrachloride,
SiCl.sub.4, may be used to increase the silicon content, but they
may leave chloride as an impurity in the product, and their
reactions may be slower than desired. Silicon amides such as
tetraisocyanatosilane, tetrakis(dimethylamido)silane or
tris(dimethylamido)silane avoid the halogen contamination. However,
their deposition rates may also be slower than desired. Silylenes
are more rapidly reactive. For example, the thermally stable
silylene 7
##STR00008##
where R is an alkyl group or, in at least some embodiments, is
tert-butyl, can be used as a rapidly reacting silicon source in
place of part or all of the metal source, in order to increase the
silicon/metal ratio.
[0057] In at least some embodiments, pure silicon dioxide may be
prepared. In an ALD system, a pulse of silylene is followed by a
pulse of oxygen gas, in order to fully oxidize the silylene after
it has reacted with the surface. Pure silicon dioxide can be
deposited rapidly by repeating the pulse sequence of silylene and
oxygen.
2. Metal Phosphate and Phosphorus Oxide
[0058] The present invention provides a method for preparing metal
phosphates of varying metal and phosphorus content. The method
involves the reaction of a vapor of an bis(alkyl)phosphate with a
vapor of one or more metal or metalloid compounds. The compound may
be formed as a powder or as a film on a substrate, and in some
embodiments, on a heated substrate. The compound may be formed on a
substrate by mixing the vapors of the bis(alkyl)phosphate and the
metal or metalloid compound prior to deposition on a substrate. In
at least some embodiments, a substrate is alternately exposed to a
bis(alkyl)phosphate vapor and a vapor of one or more of a metal or
metalloid compound.
[0059] Bis(alkyl)phosphate reactants are commercially available or
may be prepared using conventional or known techniques. Phosphorus
precursor, diethylphosphate, is commercially available from a
number of chemical companies, including Fisher Scientific
(Pittsburgh, Pa.) and Pfaltz and Bauer (Waterbury, Conn.).
Diethylphosphate may be prepared by the air oxidation of phosphinic
acid in ethanol, catalyzed by copper chloride:
.sub.2P(O)OH+2EtOH+O.sub.2.fwdarw.(EtO).sub.2P(O)OH+2H.sub.2O
(4)
See, Y. Okamoto, T. Kusano and S. Takamuku, Phosphorus, Sulfur and
Silicon, volume 55, pages 195-200 (1991).
[0060] An alternative reaction sequence is shown for
diisopropylphosphate and may be used for other precursor compounds
by appropriate substitutions for isopropanol.
PCl.sub.3+3.sup.iPrOH.fwdarw.(iPrO).sub.2P(O)H+.sup.iPrCl+2HCl
(5)
(.sup.iPrO).sub.2P(O)H+SO.sub.2Cl.sub.2.fwdarw.(.sup.iPrO).sub.2P(O)Cl+H-
Cl+SO.sub.2 (6)
(.sup.iPrO).sub.2P(O)Cl+H.sub.2O.fwdarw.(.sup.iPrO).sub.2P(O)OH+HCl
(7)
See, Melvor et al., Canadian J. Chemistry, volume 34, pages 1825
and 1827.
[0061] Diisopropylphosphate may also be prepared by first forming
its potassium salt by the following two reactions:
PCl.sub.3+3.sup.iPrOH.fwdarw.(.sup.iPrO).sub.2P(O)H+.sup.iPrCl+2HCl
(8)
(.sup.iPrO).sub.2P(O)H+KMnO.sub.4+KHCO.sub.3.fwdarw.2(.sup.iPrO).sub.2P(-
O)OK+MnO.sub.2 (9)
See, A. Zwierak and M. Kluba, Tetrahedron, volume 27, pages 3163 to
3170 (1971). The analogous sodium salt may be prepared by the
following two reactions:
POCl.sub.3+3.sup.iPrOH.fwdarw.(.sup.iPrO).sub.3P.dbd.O+3HCl
(10)
(.sup.iPrO).sub.3P.dbd.O+NaOH.fwdarw.(.sup.iPrO).sub.2P(O)ONa+.sup.iPrOH
(11)
The precursor diisopropylphosphate may then be liberated from its
alkali salt by reaction with hydrochloric acid:
(.sup.iPrO).sub.2P(O)OM+HCl.fwdarw.(.sup.iPrO).sub.2P(O)OH+MCl,
M=Na,K (12)
[0062] The above bis(alkyl)phosphates react with a wide range of
metal compounds to form metal phosphates. Metal compounds that
generally react with the acid phosphate protons include most metal
alkyls and other organometallic compounds, metal alkylamides, and
some metal alkoxides. The reactivity of any particular compound can
be established readily by mixing it with a bis(alkyl)phosphate and
analyzing the mixture for products by techniques such as nuclear
magnetic resonance (NMR).
[0063] The reaction is carried out in the vapor state and may be
carried out using CVD or ALD techniques. As is discussed in greater
detail below, ALD provides control over the deposition process and
is suitable for use in a wide range of reaction conditions and
reactant reactivity.
[0064] The phosphorus/metal ratio may be increased by replacing
some or all of the metal precursor by a suitably reactive
phosphorus compound. Phosphorus halides such as phosphorus
trichloride, PCl.sub.3, phosphorus pentachloride, PCl.sub.5, or
phosphorus oxychloride, POCl.sub.3, may be used, but some halogen
impurity may be included in the film. Phosphorus alkylamides such
as hexamethylphosphorus triamide, (Me.sub.2N).sub.3P,
hexamethylphosphorimidic triamide, (Me.sub.2N)3P.dbd.NH, or
hexamethylphosphoramide, (Me.sub.2N).sub.3PO, avoid the halogen
contamination, but their reactions may be slow. White phosphorus,
P.sub.4, and phosphorus(III) oxide, P.sub.4O.sub.6, are more
quickly reactive and can be used to increase the phosphorus/metal
ratio in an ALD process. Doses of white phosphorus or
phosphorus(III) oxide generally are followed by a pulse of oxygen
in order to form fully oxidized films.
[0065] The phosphorus/metal ratio of material made by ALD may be
decreased by replacing some of the phosphorus doses by doses of
water or alcohol.
3. Metal Amides, Metal Alkyls and Metal Alkoxides
[0066] In at least some embodiments, metal or metalloid amides are
useful in the practice of this invention. Some examples are given
in Table 1, as well as a commercial source and/or literature
references for their synthesis. The metalloids referred to in Table
1 are boron, silicon and arsenic.
TABLE-US-00001 TABLE 1 Some Volatile Metal or Metalloid Amides
Melt. Pt. Vapor Press. Compound .degree. C. .degree. C./Torr
Reference and/or commercial source Al(N(SiMe.sub.3).sub.2).sub.3
188 Waimagat, J. Organomet. Chem. 33, 1 (1971)
Al.sub.2(NEt.sub.2).sub.6 liquid Barry & Gordon, 2000
Al.sub.2(NEtMe).sub.6 liquid 100/0.25 Barry & Gordon, 2000
Al(N.sup.iPr.sub.2).sub.3 56-59 Brothers, Organometallics 13, 2792
(1994) Al.sub.2(NMe.sub.2).sub.6 88-89 90/0.1 Ruff, JACS 83, 2835
(1961) Al(N(Et)CH.sub.2CH.sub.2NMe.sub.2)(NMe.sub.2).sub.2 liquid
65-70/0.3 Barry, Gordon & Wagner, Mat. Res. Soc. Symp. Proc.
606, 83-89 (2000) As(NMe.sub.2).sub.3 -53 55/10 Cowley, JACS 95,
6505 (1973) As(N(Me)(SiMe.sub.3)).sub.3 11-13 67-70/0.1 Birkofer
& Ritter, Chem. Ber. 93, 424 (1960) B(NMe.sub.2).sub.3 -10
39/10 Abel et al., J. Chem. Soc. 1964, 5584 B(NEt.sub.2).sub.3
95/11 Abel & Armitage J. Organomet. Chem. 5, 326 (1966)
Ba(N(SiMe.sub.3).sub.2).sub.2 >150 Westerhauser, Inorg. Chem.
30, 96 (1991) Be(NMe.sub.2).sub.2 88-90 175/760 Anderson, JACS 74,
1421 (1952) Be(N(SiMe.sub.3).sub.2).sub.2 -5, liquid 110/3 Clark
& Haaland, Chem. Commun., 1969, 912 Be(TMPD).sub.2 -10, liquid
106/0.001 Noeth & Schlosser, Inorg. Chem. 22, 2700 (1983)
Bi(N(SiMe.sub.3).sub.2).sub.3 90 Lappert, J. Chem. Soc, Dalton,
2428 (1980) Bi(N(Me)(SiMe.sub.3)).sub.3 90-92/0.1 Birkofer &
Ritter, Chem. Ber. 93, 424 (1960) Ca(N(SiMe.sub.3).sub.2).sub.2
>120 Lappert, J. Chem. Soc, Chem. Comm., 1141 (1990)
Cd(N(SiMe.sub.3).sub.2).sub.2 liquid Burger, Wannagat, J.
Organomet. Chem. 3, 11 (1965) Cd(N.sup.tBuSiMe.sub.3).sub.2 Fisher
& Alyea, Polyhedron 3, 509 (1984) Cd(TMPD).sub.2 Fisher &
Alyea, Polyhedron 3, 509 (1984) Ce(N(SiMe.sub.3).sub.2).sub.3
95-100/10.sup.-4 Bradley, J. Chem. Soc, Dalton 1973, 1021
Ce(N.sup.iPr.sub.2).sub.3 Angew. Chem., Int. Ed. Engl. 36, 2480
(1997) Co(N(SiBuMe.sub.2).sub.2).sub.2 liquid 146/0.085
Broomhall-Dillard & Gordon, 1999
Co(N(SiEtMe.sub.2).sub.2).sub.2 liquid 106/0.05 Broomhall-Dillard
& Gordon, 1999 Co(N(SiMe.sub.3).sub.2).sub.2 >70 50-70/0.01
Chisholm, CVD 1, 49 (1995) Co(N(SiMe.sub.3).sub.2).sub.3 86-88
Power, JACS 11, 8044 (1989) Co(N(SiPrMe.sub.2).sub.2).sub.2 liquid
106/0.05 Broomhall-Dillard & Gordon, 1999
Cr(N(SiMe.sub.3).sub.2).sub.3 120 80/0.005 Bradley, J. Chem. Soc,
Dalton 1972, 1580 Cr(Net.sub.2).sub.4 liquid 40-60/10.sup.-3
Bradley, Proc. Chem. Soc, London 1963, 305
Cr(N.sup.iPr.sub.2).sub.3 Bradley & Chisholm, Chem. Comm. 1968,
495 Cr(NMe.sub.2).sub.4 Bradley, J. Chem. Soc. A, 1971, 1433
Cu.sub.4(N(SiMe.sub.3).sub.2).sub.4 .sup. >180(d.) 160/0.1
Chisholm, CVD 1, 49 (1995) Er(N(SiMe.sub.3).sub.2).sub.3 150-180
Wolczanski, Inorg. Chem. 31, 1311 (1992)
Eu(N(SiMe.sub.3).sub.2).sub.3 160-162 82-84/10.sup.-4 Bradley,
Chem. Comm. 1972, 349 Fe(N(SiBuMe.sub.2).sub.2).sub.2 liquid
130/0.2 Broomhall-Dillard & Gordon, 1999
Fe(N(SiMe.sub.3).sub.2).sub.2 5, liquid 80-90/0.01 Chisholm, CVD 1,
49 (1995) Fe(N(SiMe.sub.3).sub.2).sub.3 >80 80/0.005 Bradley, J.
Chem. Soc, Dalton 1972, 1580 Ga(NMe.sub.2).sub.3 91 125/0.01 Chemat
Catalog, Northridge, CA Ga(NEt.sub.2).sub.3 Chemat Catalog,
Northridge, CA Ga(N(SiMe.sub.3).sub.2).sub.3 187 Wannagat, J.
Organomet. Chem. 33, 1 (1971) Ga(N.sup.tBuSiMe.sub.3).sub.3 174-176
Cowley, Inorg. Chem. 33, 3251 (1994) Ga(TMPD).sub.3 130-132 Cowley,
Inorg. Chem. 33, 3251 (1994)
Ga(N(Me)CH.sub.2CH.sub.2NMe.sub.2)(NMe.sub.2).sub.2 liquid
48-55/0.18 Barry, Gordon & Wagner, Mat. Res. Soc. Symp. Proc.
606, 83-89 (2000) Gd(N(SiMe.sub.3).sub.2).sub.3 160-163
80-83/10.sup.-4 Bradley, Chem. Comm. 1972, 349
Ge(N(SiMe.sub.3).sub.2).sub.2 33 60/0.04 Chisholm, CVD 1, 49 (1995)
Ge(NEt.sub.2).sub.4 >109 109/2 Chemat Catalog, Northridge, CA
Ge(NMe.sub.2).sub.4 14, liquid 203/760 Abel, J. Chem. Soc. 1961,
4933; Chemat Ge(N.sup.tBu.sub.2).sub.2 2, liquid Lappert, J. Chem.
Soc, Chem. Com.13, 621 (1980) Ge(N.sup.tBuSiMe.sub.3).sub.2 22
50/0.04 Lappert, J. Chem. Soc, Dalton Trans. 1977, 2004
Ge(TMPD).sub.2 60-62 70/0.02 Lappert, J. Chem. Soc., Chem. Com. 13,
621 (1980) Hf(NEt.sub.2).sub.4 liquid 100/0.84 Bradley, J. Chem.
Soc A, 1969, 980 Hf(NEtMe).sub.4 liquid 83/0.05 Becker &
Gordon, 2000; Aldrich Hf(NMe.sub.2).sub.4 30 70/0.73 Bradley, J.
Chem. Soc. A, 1969, 980 Hg(N(SiMe.sub.3).sub.2).sub.2 liquid
Earborn, J. Chem. Soc, Chem. Comm., 1051 (1968)
Ho(N(SiMe.sub.3).sub.2).sub.3 161-164 80-85/10.sup.-4 Bradley, J.
Chem. Soc, Dalton 1973, 1021 In(N(SiMe.sub.3).sub.2).sub.3 168
Wannagat, J. Organomet. Chem. 33, 1 (1971) In(TMPD).sub.3 Frey et
al., Z. Anorg. Allg. Chem. 622, 1060 (1996) KN(SiHexMe.sub.2).sub.2
liquid Broomhall-Dillard, Mater. Res. Soc. 606, 139 (2000)
KN(SiMe.sub.3).sub.2 90-100/10.sup.-3 Fieser & Fieser 4, 407
La(N(SiMe.sub.3).sub.2)3 145-149 100/10.sup.-4 Bradley, J. Chem.
Soc, Dalton 1973, 1021 La(N.sup.tBuSiMe.sub.3)3 146-147
90-95/10.sup.-4 Becker, Suh & Gordon, 2000
La(N.sup.iPr.sub.2).sub.3 Aspinall, J. Chem. Soc, Dalton 1993, 993
La(TMPD).sub.3 137-139 100/10.sup.-4 Suh & Gordon, 2000
LiN(SiEtMe.sub.2).sub.2 liquid 123/0.2 Broomhall-Dillard, Mater.
Res. Soc. 606, 139 (2000) LiN(SiMe.sub.3).sub.2 71-72 115/1 Inorg.
Synth. 8, 19 (1966) Li(TMPD) Kopka, J. Org. Chem. 52, 448 (1987)
Lu(N(SiMe.sub.3).sub.2).sub.3 167-170 75-80/10.sup.-4 Bradley,
Chem. Comm. 1972, 349 Mg(N(SiMe.sub.3).sub.2).sub.2 123 Andersen,
.!.Chem. Soc, Dalton Trans. 1982, 887 Mg(TMPD).sub.2 Eaton, JACS
111, 8016 (1989) Mn(N(SiBuMe.sub.2).sub.2).sub.2 liquid 143/0.06
Broomhall-Dillard & Gordon, 1999 Mn(N(SiMe.sub.3).sub.2).sub.2
55-60 112-120/0.2 Bradley, Trans. Met. Chem. 3, 253 (1978)
Mn(N(SiMe.sub.3).sub.2).sub.3 108-110 Power, JACS 11, 8044 (1989)
Mo(N.sup.tBuSiMe.sub.3).sub.3 Laplaza, Cummins, JACS 118, 8623
(1996) Mo.sub.2(NEt.sub.2).sub.6 Chisholm, JACS 98, 4469 (1976)
Mo.sub.2(NMe.sub.2).sub.6 solid 100/10.sup.-4 Chisholm, JACS 98,
4469 (1976) Mo(NEt.sub.2).sub.4 liquid 80-110/10.sup.-4 Bradley
& Chisholm, J. Chem. Soc. A 1971, 2741 Mo(NMe.sub.2).sub.4
solid 40-70/0.1 Bradley & Chisholm, J. Chem. Soc. A 1971, 2741
NaN(Si.sup.nBuMe.sub.2).sub.2 liquid 189/0.08 Broomhall-Dillard,
Mater. Res. Soc. 606, 139 (2000) NaN(SiMe.sub.3).sub.2 171-175
170/2 Chem. Ber. 94, 1540 (1961) Nb(N(SiMe.sub.3).sub.2).sub.3
solid Broomhall-Dillard & Gordon, 1998 Nb(NEt.sub.2).sub.4
liquid Bradley & Thomas, Can. J. Chem. 40, 449 (1962)
Nb(NEt.sub.2).sub.5 >120 120/0.1 Bradley & Thomas, Can. J.
Chem. 40, 449 (1962) Nb(NMe.sub.2).sub.5 >100 100/0.1 Bradley
& Thomas, Can. J. Chem. 40, 449 (1962)
Nd(N(SiMe.sub.3).sub.2).sub.3 161-164 85-90/10.sup.-4 Bradley, J.
Chem. Soc, Dalton 1973, 1021 Nd(N.sup.iPr.sub.2).sub.3 Bradley,
Inorg. Nucl. Chem. Lett. 12, 735 (1976)
Ni(N(SiMe.sub.3).sub.2).sub.2 liquid 80/0.2 Burger & Wannagat,
Mh. Chem. 95, 1099 (1964) Pb(N(SiMe.sub.3).sub.2).sub.2 39 60/0.04
Lappert, J. Chem. Soc, Chem. Com. 16, 776 (1980)
Pb(N.sup.tBuSiMe.sub.3).sub.2 22 50/0.04 Lappert, J. Chem. Soc,
Dalton Trans. 1977, 2004 Pr(N(SiMe.sub.3).sub.2).sub.3 155-158
88-90/10''.sup.4 Bradley, Chem. Comm. 1972, 349 Sb(NMe.sub.2).sub.3
liquid 50/0.5 Cowley, JACS 95, 6506 (1973)
Sb(N(Me)(SiMe.sub.3)).sub.3 9-11 78-79/0.1 Birkofer & Ritter,
Chem. Ber. 93, 424 (1960) Sc(N(SiMe.sub.3).sub.2).sub.3 172-174
Bradley, J. Chem. Soc, Dalton 1972, 1580 SiH.sub.2(NMe.sub.2).sub.2
-104 93/760 Anderson et al., J. Chem. Soc. Dalton 12, 3061 (1987)
SiH(NMe.sub.2).sub.3 -90 62/45 Gelest, Pfaltz & Bauer, Strem
Catalogs Si(NMe.sub.2).sub.4 1-2 196/760 Gordon, Hoffman &
Riaz, Chem. Mater. 2, 480 (1990) Si(NHMe).sub.4 37 45/0.05
Schmisbaur, Inorg. Chem. 37, 510 (1998) Si(NHn-Pr).sub.4 liquid
75/0.05 Schmisbaur, Inorg. Chem. 37, 510 (1998) Si(NEt.sub.2).sub.4
3-4 74/19 Abel et al., J. Chem. Soc. 1965, 62; Chemat Si(NCO).sub.4
25-26 40/1 Forbes & Anderson, JACS 62, 761 (1940); Gelest,
Petrarch, Showa-Denko Si(NCO).sub.4 25-26 40/1 Forbes &
Anderson, JACS 62, 761 (1940); Gelest, Petrarch, Showa-Denko
Sm(N(SiMe.sub.3).sub.2).sub.3 155-158 83-84/10.sup.-4 Bradley,
Chem. Comm. 1972, 349 Sn(N(SiMe.sub.3).sub.2).sub.2 38 84/0.04
Chisholm, CVD 1, 49 (1995) Sn(NEt.sub.2).sub.4 liquid 90/0.05 Jones
& Lappert, J. Chem. Soc. 1965, 1944 Sn(NMe.sub.2).sub.4 liquid
51/0.15 Jones & Lappert, J. Chem. Soc. 1965, 1944
Sn(N.sup.tBu.sub.2).sub.2 47 Lappert, J. Chem. Soc, Chem. Com. 13,
621 (1980) Sn(N.sup.tBu.sub.2).sub.3 Hudson, J. Chem. Soc. Dalton
Trans. 1976, 2369 Sn(N.sup.tBuSiMe.sub.3).sub.2 19, liquid 50/0.04
Lappert, J. Chem. Soc, Dalton Trans. 1977, 2004
Sn(N.sup.tBuSiMe.sub.3).sub.3 Hudson, J. Chem. Soc. Dalton Trans.
1976, 2369 Sn(TMPD).sub.2 Lappert, J. Chem. Soc, Chem. Com. 16, 776
(1980) Sr(N(SiMe.sub.3).sub.2).sub.2 164 Westerhauser, Inorg. Chem.
30, 96 (1991) Ta(NEt.sub.2).sub.4 120/0.1 Bradley & Thomas,
Can. J. Chem. 40, 1355 (1962) Ta(NMe.sub.2).sub.5 >180 100/0.1
Bradley & Thomas, Can. J. Chem. 40, 1355 (1962); Strem
Ta(N.sup.tBu)(NEt.sub.2).sub.3 liquid .sup. 90/0. i Inorgtech
Ta(NEt)(NEt.sub.2).sub.3 liquid 120/0.1 Becke-Goehring &
Wunsch, Chem. Ber. 93, 326 (1960) Tb(N(SiMe.sub.3).sub.2).sub.3
162-165 78-82/10.sup.-4 Wolczanski, Inorg. Chem. 31, 1311 (1992)
Th(NEt.sub.2).sub.4 40-50/10.sup.-4 Reynolds & Edelstein,
Inorg. Chem. 16, 2822 (1977) Th(NPr.sub.2).sub.4 liquid
60-70/10.sup.-4 Reynolds & Edelstein, Inorg. Chem. 16, 2822
(1977) Ti(N(SiMe.sub.3).sub.2).sub.3 solid Bradley, J. Chem. Soc,
Dalton 1972, 1580 Ti(N.English Pound.t.sub.2).sub.4 liquid 112/0.1
Bradley & Thomas, J. Chem. Soc. 1960, 3857 Ti(N'Pr.sub.2).sub.3
Kruse, Inorg. Chem. 9, 2615 (1970) Ti(N'Pr.sub.2).sub.4 82-85
110/0.001 Froneman, P, S, Si, Relat. Elem. 47, 273 (1990)
Ti(NMe.sub.2).sub.4 liquid 50/0.05 Bradley & Thomas, J. Chem.
Soc 1960, 3857 Tl(N(SiMe.sub.3).sub.2).sub.3 Allman, J. Organomet.
Chem. 162, 283 (1978) U(N(SiMe.sub.3).sub.2).sub.3 137-140
80-100/10.sup.-3 Andersen, Inorg. Chem. 18, 1507 (1979)
U(NEt.sub.2).sub.4 115-125/.06 Jones, JACS 78, 4285 (1956)
U(NPr.sub.2).sub.4 liquid 40-50/10.sup.-4 Reynolds & Edelstein,
Inorg. Chem. 16, 2822 (1977) V(N(SiMe.sub.3).sub.2).sub.3 >95
95/0.005 Bradley, J. Chem. Soc, Dalton 1972, 1580
V(NEt.sub.2).sub.4 liquid 90/0.001 Bradley, Chem. Commun. 1964,
1064
V(NMe.sub.2).sub.4 solid 50/0.001 Bradley, J. Chem. Soc A, 1969,
2330 V(O)(NMe.sub.2).sub.3 40 40/0.001 Davidson, Harris &
Lappert, JCS Dalton 1976, 2268 W.sub.2(NEt.sub.2).sub.6 solid
140-170/10.sup.-4 Chisholm, JACS 97, 5626 (1975); 98, 4477 (1976)
W.sub.2(NMeEt).sub.6 solid 100-130/10.sup.-4 Burger & Wannagat,
Monatsh. 95, 1099 (1964) W.sub.2(NMe.sub.2).sub.6 solid
100-120/10.sup.-4 Burger & Wannagat, Monatsh. 95, 1099 (1964)
W(N.sup.tBu).sub.2(NH.sup.tBu).sub.2 89-90 60-65/10.sup.-4 Nugent
& Harlow, Inorg. Chem. 19, 777 (1980)
W(N.sup.tBu).sub.2(NEtMe).sub.2 liquid 87/0.1 Suh & Gordon,
2000 W(N.sup.tBu).sub.2(NMe.sub.2).sub.2 liquid 75/0.1 Suh &
Gordon, 2000 Y(N(SiMe.sub.3).sub.2).sub.3 180-184 100/10.sup.-4
Bradley, J. Chem. Soc, Dalton 1973, 1021; Alfa
Y(N.sup.iPr.sub.2).sub.3 Bradley, Inorg. Nucl. Chem. Lett. 12, 735
(1976) Y(N.sup.tBuSiMe.sub.3)3 158-160 90-95/10.sup.-4 Suh &
Gordon, 2000 Y(TMPD).sub.3 177-179 100/10.sup.-4 Suh & Gordon,
2000 Yb(N(SiMe.sub.3).sub.2).sub.3 162-165 Bradley, J. Chem. Soc,
Dalton 1973, 1021 Yb(N.sup.1Pr.sub.2).sub.3 Bradley, Inorg. Nucl.
Chem. Lett. 12, 735 (1976) Zn(N(SiMe.sub.3).sub.2).sub.2 liquid
120/0.1 Inorg. Chem. 23, 1972 (1984) Zn(N.sup.tBu.sub.2).sub.2
Schumann, Z. Anorg. Allg. Chem. 623, 1881 (1997) Zn(TMPD).sub.2
Schumann, Z. Anorg. Allg. Chem. 623, 1881 (1997)
Zr(NEt.sub.2).sub.4 liquid 112/0.1 Bradley & Thomas, .1. Chem.
Soc. 1960, 3857 Zr(NEtMe).sub.4 liquid 82/0.05 Becker & Gordon,
2000 Zr(N.sup.iPr.sub.2).sub.4 >120 120/0.001 Bradley, Inorg.
Nucl. Chem. Lett. 11, 155 (1975) Zr(NMe.sub.2).sub.4 70 65-80/0.1
Bradley & Thomas, J. Chem. Soc. 1960, 3857
In Table 1, TMPD stands for 2,2,6,6-tetramethylpiperidide. Further
examples may be found in the book Metal and Metalloid Amides, by M.
F. Lappert, P. P. Power, A. R. Sanger and R. C. Srivastava,
published in 1980 by Ellis Horwood Ltd., a division of John Wiley
& Sons.
[0067] In at least some embodiments, metal alkyls are useful in the
practice of this invention. Some examples are given in Table 2, as
well as a commercial source or literature reference of their
synthesis.
TABLE-US-00002 TABLE 2 Some Volatile Organometallic Compounds Melt.
Pt. Vapor Press. Compound .degree. C. .degree. C./Torr Sources
AlMe.sub.3 15.4 20/8 Strem Ba(n-PrMe.sub.4Cp).sub.2 liquid Strem
Ba(.sup.iPr.sub.4Cp).sub.2 149-150 90/0.01 J. Am. Chem. Soc. 113,
4843-4851 (1991) Ba(Me.sub.5Cp).sub.2 265-268 140/0.01 J.
Organomet. Chem. 325, 31-37 (1987) BeEt.sub.2 12, liquid 110/15
Strem BiMe.sub.3 liquid 110/760 Pfaltz & Bauer, Organometallics
Ca(.sup.iPr.sub.4Cp).sub.2 196-200 190/0.01 J. Am. Chem. Soc. 113,
4843-4851 (1991) Ca(Me.sub.5Cp).sub.2 207-210 90/0.01 J. Organomet.
Chem. 325, 31-37 (1987) CdMe.sub.2 -4.5 105.5/760 Strem CeCp.sub.3
452 230/0.01 Strem Ce(.sup.iPrCp).sub.3 Strem Ce(Me.sub.4Cp).sub.3
solid Aldrich CoCp.sub.2 176-180 Aldrich, Strem CoCp(CO).sub.2
liquid 37-38.5/2 Strem Co(CO).sub.3NO liquid 50/760 Strem
CrCp.sub.2 168-170 Aldrich, Strem Cr(Me.sub.5Cp).sub.2 200 Strem
Cr(.sup.iPrCp).sub.2 solid Strem Cr(EtBz).sub.2 liquid 140-160/1
Strem CuCpPEt.sub.3 solid 60/0.01 Strem Er(Cp).sub.3 285 200/0.01
Strem Er(.sup.iPrCp).sub.3 63-65 222/10 Aldrich, Alfa, Strem
Er(BuCp).sub.3 liquid 240/0.1 Aldrich, Alfa (pyrophoric)
Eu(Me.sub.4Cp).sub.3 solid Aldrich FeCp(Me.sub.2NCH.sub.2Cp) liquid
91-92/0.5 Strem FeCp(.sup.iBuCp) liquid 80/0.15 Strem GaMe.sub.3
-15, 55.7/760 Strem liquid GdCp.sub.3 295 Aldrich, Alfa, Strem
Gd(.sup.iPrCp).sub.3 liquid 200/0.01 Erbil, U.S. Pat. No. 4,882,206
(1989) InCp.sub.3 solid 50/0.01 Strem In(Me.sub.5Cp).sub.3 Strem
InMe.sub.3 88 Strem Ir(MeCp)(1,5-COD) Strem La(.sup.1PrCp).sub.3
liquid 180-195/0.01 Strem; Erbil, U.S. Pat. No. 4,882,206 (1989)
LaCp.sub.3 295 dec. 218/0.1 Aldrich, Alfa, Strem
LaCp.sub.3(NCCH.sub.3).sub.2 162 Inorganica Chim. Acta 100, 183-199
(1985) La(Me.sub.2NC.sub.2H.sub.4Cp).sub.3 75 160/0.001 J.
Organomet. Chem. 462, 163-174 (1993) Mg(PrCp).sub.2 liquid Strem
Mg(EtCp).sub.2 liquid Aldrich, Strem MgCp.sub.2 180 160/0.1
Aldrich, Strem MnCp.sub.2 175 Aldrich, Strem Mn(EtCp).sub.2 liquid
Aldrich (pyrophoric) Mn(Me.sub.5Cp).sub.2 292 Strem Mo(EtBz).sub.2
liquid Strem NdCp.sub.3 417 220/0.01 Aldrich, Alfa, Strem
Nd(.sup.iPrCp).sub.3 solid Aldrich, Alfa, Strem Ni(PF.sub.3).sub.4
liquid 70.7/760 Strem PrCp.sub.3 427 220/0.01 Aldrich, Alfa, Strem
Pr(.sup.iPrCp).sub.3 50-54 Aldrich, Alfa, Strem SbEt.sub.3 156/760
Strem ScCp.sub.3 240 200/0.05 Aldrich, Strem SmCp.sub.3 356
220/0.01 Strem Sm(.sup.iPrCp).sub.3 Zh. Neorg. Khim. 27, 2231-4
(1982) Sr(.sup.iPr.sub.4Cp).sub.2 151-153 Chem. Rev. 93, 1023-1-36
(1993) Sr(Me.sub.5Cp).sub.2 216-218 J. Organomet. Chem. 325, 31-37
(1987) solid Aldrich, Strem TmCp.sub.3 solid Strem
Tm(.sup.iPrCp).sub.3 MRS Symp. Proc. 301, 3-13 (1993) TICp solid
75/0.1 Strem VCp.sub.2 165-167 200/0.1 Aldrich, Strem V(EtCp).sub.2
liquid Aldrich W(.sup.1PrCp).sub.2H.sub.2 liquid 122-125/0.1
Aldrich, Strem YCp.sub.3 296 200/2 Alfa, Strem Y(MeCp).sub.3 Strem
Y(.sup.nPrCp).sub.3 Strem Y(BuCp).sub.3 liquid Aldrich, Alfa, Strem
YbCp.sub.3 277 150(vac.) Strem Yb(.sup.iPrCp).sub.3 47 Zh. Neorg.
Khim. 27, 2231-4 (1982) ZnEt.sub.2 -28, 124/760 Aldrich, Strem
liquid ZnMe.sub.2 -42, 46/760 Aldrich, Strem liquid
ZrCp.sub.2Me.sub.2 170 Aldrich, Strem Zr(.sup.tBuCp).sub.2Me.sub.2
Strem
In Table 2, Cp is an abbreviation for cyclopentadienide, Me.sub.5Cp
represents pentamethylcyclopentadienide, .sup.iPrCp represents
isopropylcyclopentadienide, .sup.iPrMe.sub.4p stands for
isopropyltetramethylcyclopentadienide, .sup.iPr.sub.4Cp stands for
tetraisopropylcyclopentadienide, EtCp stands for
ethylcyclopentadienide, PrCp stands for propylcyclopentadienide,
.sup.iPrCp stands for isopropylcyclopentadienide, BuCp stands for
butylcyclopentadienide, Bz for benzenide, EtBz for a mixture of
isomers of ethylbenzenide and 1,5-COD for 1,5-cyclooctadienide.
[0068] In at least some embodiments, metal or metalloid alkoxides
can be used in the practice of this invention. Suitable compounds
are listed in Table 3, as well as a commercial source or a
literature reference of their synthesis.
TABLE-US-00003 TABLE 3 Some Volatile Metal or Metalloid Alkoxides
Melt. Pt. Vapor Press. Compound .degree. C. .degree. C./Torr
Sources Al.sub.2Et.sub.3(O-sec-Bu).sub.3 liquid 190/0.1 Strem
B(OMe).sub.3 -29, liquid 68.7/760 Aldrich, Rohm and Haas, Strem
Hf(O.sup.tBu).sub.4 liquid 90/5 Strem Nb(OEt).sub.5 6, liquid
156/0.05 Aldrich, Chemat, Strem Ta(OEt).sub.5 21 146/0.15 Aldrich,
Chemat, Strem Ti(O.sup.iPr).sub.4 20 58/1 Aldrich, Chemat, DuPont,
Strem Y(OCMe.sub.2CH.sub.2NMe.sub.2).sub.3 liquid 80/0.001
Herrmann, Inorg. Chem. 36, 3545-3552(1997) Zr(O.sup.tBu).sub.4
liquid 81/3, 90/5 Aldrich, Strem
Metal halides may also be used in the practice of this invention,
but they have the disadvantages that they tend to leave some halide
impurity in the film and cause corrosion of substrates or
apparatus.
4. Reactions with Water and Alcohols
[0069] In at least some embodiments, part of the silanol or
phosphate is replaced with water in order to deposit metal-rich
silicates and phosphates. In a CVD reactor, water vapor tends to
react very quickly with the vapors of the metal precursors near the
vapor entrance to produce powder, rather than film on the
substrate. In an ALD reactor such premature reactions are avoided
because the reactants are introduced alternately into the reactor,
so reactions near the entrance are prevented and reaction is
confined to the surface of the substrate. However, water tends to
adsorb strongly on surfaces, so it can take a long time to purge
the ALD reactor between pulses of the reactants.
[0070] Alcohols such as isopropanol and tert-butanol can alleviate
these problems with water, since the reactions of alcohols with
metal compounds are slower, and the more volatile alcohols can be
pumped more quickly from an ALD reactor. Alcohols such as
isopropanol and tert-butanol are particularly appropriate for
reactions involving thermally liable metal compounds. In some cases
the substrate temperature is raised in order to decompose alkyl
alcohols and thereby remove their carbon content from the film. A
thermally labile metal compound may self-decompose at higher
substrate temperatures, so self-limiting ALD reactions cannot be
achieved.
[0071] The arene hydrates are a class of alcohols that decompose at
lower temperatures than ordinary alkyl alcohols, and thus can be
used to provide carbon-free metal oxides at low enough temperatures
to avoid self-decomposition of even thermally labile metal
compounds. For example, benzene hydrate decomposes easily to water
and benzene because of the aromatic stabilization of the benzene
byproduct:
##STR00009##
Other examples of useful arene hydrates are alkyl-substituted
benzene hydrates such as the various isomers of toluene
hydrate:
##STR00010##
Other useful alcohols include the two naphthalene hydrates
##STR00011##
and alkyl-substituted naphthalene hydrates such as methyl
naphthalene hydrate. Thus arene alcohols may be used in the
reaction of metal compounds at moderate deposition conditions. In
particular, it can be used for the formation of metal oxides, or
for the formation of metal silicates or metal phosphates when used
in combination with the silicon and phosphorus precursors described
herein.
[0072] In at least some embodiments of the present invention, a
metal oxide is obtained by reaction of a metal amide with water.
Suitable metal amides include any of those listed in Table 1. Thus,
by way of example, hafnium oxide was prepared by ALD using water
vapor and tetrakis(dimethylamido)hafnium. This ALD reaction was
found to be surprisingly efficient, in that almost all of the
precursor that was delivered into the reaction chamber was
deposited as film on the substrate and on the exposed wall of the
chamber. It was also found to be surprisingly fast, going to
completion (saturation of the surface reaction on a flat surface)
with less than 50 Langmuirs of vapor flux (1 Langmuir is the flux
delivered to a surface in one second by a partial pressure of
10.sup.-6 Torr of the precursor). The byproducts of the reaction
were found to consist of dimethylamine vapor, which does not etch
the deposited hafnium oxide film. Most surprisingly, the use of
tetrakis(alkylamido)hafnium precursors succeeded in the ALD of
highly uniform films of hafnium oxide even in holes with very high
aspect rations (over 40). By way of contrast, the reactants
commonly used in the prior art for ALD of hafnium oxide, HfCl.sub.4
and Hf(O-tert-Bu).sub.4, have not succeeded in the uniform
deposition of HfO.sub.2 in holes with such high aspect ratios.
[0073] Vaporization of Reactants and Product Deposition.
[0074] Vapors of liquid precursors may be formed by conventional
methods, including heating in a bubbler, in a thin-film evaporator,
or by nebulization into a carrier gas preheated to about 100 to
250.degree. C. The nebulization may be carried out pneumatically or
ultrasonically. Solid precursors may be dissolved in organic
solvents, including hydrocarbons such as decane, dodecane,
tetradecane, toluene, xylene and mesitylene, and with ethers,
esters, ketones and chlorinated hydrocarbons. Solutions of liquid
precursors generally have lower viscosities than the pure liquids,
so that in some cases it may be preferable to nebulize and
evaporate solutions rather than the pure liquids. The liquids or
solutions can also be evaporated with thin-film evaporators or by
direct injection of the liquids into a heated zone. Thin-film
evaporators are made by Artisan Industries (Waltham, Mass.).
Commercial equipment for direct vaporization of liquids is made by
MKS Instruments (Andover, Mass.), ATMI, Inc. (Danbury, Conn.),
Novellus Systems, Inc. (San Jose, Calif.) and COVA Technologies
(Colorado Springs, Colo.). Ultrasonic nebulizers are made by
Sonotek Corporation (Milton, N.Y.) and Cetac Technologies (Omaha,
Nebr.).
[0075] The silicon precursors of the present invention may be
reacted with metal or metalloid amides, such as those in Table 1,
to form metal or metalloid silicates. The silicon precursors of the
present invention may be reacted with organometallic compounds,
such as those in Table 2, to form metal silicates. The silicon
precursors of the present invention may be reacted with metal or
metalloid alkoxides, such as those in Table 3, to form metal or
metalloid silicates. The silicon precursors of the present
invention may also be reacted with other suitably reactive metal
compounds to form metal silicates. For example,
tris(tert-butoxy)silanol may be reacted with
tris(tert-butyl(trimethylsilyl)amido)yttrium (Table 1) to form
yttrium silicate (Examples 5 and 6). Also, tris(tert-butoxy)silanol
may be reacted with tris(tert-butyl(trimethylsilyl)amido)lanthanum
(Table 1) to form lanthanum silicate (Examples 7 and 8). Metal
oxides may be obtained by reaction of a suitable metal and with
water. Tris(bis(trimethylsilyl)amido)lanthanum reacts with water
vapor to form a more lanthanum-rich silicate (Example 21).
Lanthanum oxide may be deposited from silicon-free precursors such
as tris(2,2,6,6-tetramethylpiperidido)lanthanum (Example 22).
[0076] The phosphorus precursors of the present invention may be
reacted with suitably reactive metal compounds, such as those in
the Tables, to form metal phosphates. For example,
diisopropylphosphate may be reacted with lithium
bis(ethyldimethylsilyl)amide (Table 1) to provide a process for
depositing lithium phosphate films that are lithium ion conductors,
as is shown in Examples 9 and 10.
[0077] The process of the invention can be carried out in standard
equipment well known in the art of chemical vapor deposition (CVD).
The CVD apparatus brings the vapors of the reactants into contact
with a heated substrate on which the material deposits. A CVD
process can operate at a variety of pressures, including in
particular normal atmospheric pressure, and also lower pressures.
Commercial atmospheric pressure CVD furnaces are made in the USA by
the Watkins-Johnson Company (Scotts Valley, Calif.), BTU
International (North Billerica, Mass.) and SierraTherm
(Watsonville, Calif.). Commercial atmospheric pressure CVD
equipment for coating glass on the float production line is made in
the USA by Pilkington North America (Toledo, Ohio), PPG Industries
(Pittsburgh, Pa.) and AFG Industries (Kingsport, Tenn.).
Low-pressure CVD equipment is made by Applied Materials (Santa
Clara, Calif.), Spire Corporation (Bedford, Mass.), Materials
Research Corporation (Gilbert, Ariz.), Novellus Systems, Inc. (San
Jose, Calif.), Genus (Sunneyvale, Calif.), Mattson Technology
(Frement, Calif.), Emcore Corporation (Somerset, N.J.), NZ Applied
Technologies (Woburn, Mass.), COVA Technologies (Colorado Springs,
Colo.) and CVC Corporation (Freemont, Calif.). Apparatus adapted to
atomic layer deposition (ALD) is available from Genus (Sunneyvale,
Calif.) and ASM Microchemistry (Espoo, Finland).
[0078] The process of the invention may also be carried out using
atomic layer deposition (ALD). ALD introduces a metered amount of a
first reactant component into a deposition chamber having a
substrate therein for layer deposition. A thin layer of the first
reactant is deposited on the substrate. After a preselected time
period, a metered amount of a second reactant component is then
introduced into the deposition chamber, which is deposited on and
interacts with the already deposited layer of the first reactant
component. Alternating layers of first and second reactant
components are introduced into the deposition chamber and deposited
on the substrate to form a layer of controlled composition and
thickness. Alternation of deposition may be on the order of seconds
to minutes and is selected to provide adequate time for the just
introduced component to deposit on the substrate and for any excess
vapor to be removed from the headspace above the substrate. It has
been determined that the surface reactions are self-limiting so
that a reproducible layer of predictable composition is deposited.
Use of more than two reactant components is within the scope of the
invention.
[0079] In at least some embodiments of the invention, automobile
fuel injectors (Ford model CM-4722 F13Z-9F593-A) may be used to
deliver pulses of the solutions of precursors into the nitrogen
carrier gas. Solution is delivered each time a valve opens for
about 50 milliseconds.
[0080] In another embodiment of the invention, 6-port sampling
valves (Valco model EP4C6WEPH, Valco Instruments, Houston, Tex.)
normally used for injecting samples into gas chromatographs may be
used to deliver pulses of solutions into a suitable carrier gas.
Each time that a valve is opened, solution flows into a tube in
which solution is vaporized by heat from hot oil flowing over the
outside of the tube. Carrier gas moves the vapor from the tube into
the ADD reactor tube.
[0081] In at least some embodiments, a layer is deposited by ALD
using an apparatus such as that illustrated in FIG. 1. According to
at least some embodiments, measured doses of reactant vapor 30 are
introduced into the heated deposition chamber 110 by the use of a
pair of air-actuated diaphragm valves, 50 and 70 (Titan II model
made by Parker-Hannifin, Richmond Calif.). The valves are connected
by a chamber 60 having a measured volume V, and this assembly is
placed inside an oven 80 held at a controlled temperature T.sub.2.
The pressure of the reactant vapor 30 in the precursor reservoir 10
is equal to the equilibrium vapor pressure P.sub.eq of the solid or
liquid reactant 20 at a temperature T.sub.1 determined by the
surrounding oven 40. The temperature T.sub.1 is chosen to be high
enough so that the precursor pressure P.sub.eq is higher than the
pressure P.sub.dep in the deposition chamber. The temperature
T.sub.2 is chosen to be higher than T.sub.1 so that only vapor and
no condensed phase is present in the valves 50 and 70 or the
chamber 60. In the case of a gaseous reactant, its pressure can be
set by a pressure regulator (not shown) that reduces its pressure
from the pressure in the precursor gas cylinder 10.
[0082] A similar arrangement is provided for each reactive
precursor introduced into the deposition chamber 110. Thus, a
precursor reservoir 11 holds a solid or liquid reactant 21 having a
vapor pressure 31 at a temperature T.sub.1' maintained by
surrounding oven 41. Valves 51 and 71 are connected by a chamber 61
having a measured volume V' and this assembly is housed in oven 81
at temperature T.sub.2'.
[0083] Carrier gas (such as nitrogen) flows at a controlled rate
into inlet 90 in order to speed the flow of the reactants into the
deposition chamber and the purging of reaction byproducts and
un-reacted reactant vapor. A static mixer may be placed in the
tubing 100 leading into the reactor, to provide a more uniform
concentration of the precursor vapor in the carrier gas as it
enters the deposition chamber 110 heated by furnace 120 and
containing one or more substrates 130. The reaction byproducts and
un-reacted reactant vapors are removed by trap 140 before passing
into a vacuum pump 150. Carrier gas exits from exhaust 160.
[0084] In operation, valve 70 is opened so that the pressure inside
chamber 60 is reduced to a value P.sub.dep close to that of the
deposition chamber 110. Then valve 70 is closed and valve 50 is
opened to admit precursor vapor from precursor reservoir 10 into
chamber 60. Then valve 50 is closed so that the volume V of chamber
60 contains vapor of the precursor at a pressure P.sub.eq. Finally,
valve 70 is opened to admit most of the precursor vapor contained
in chamber 60 into the deposition chamber. The number of moles, n,
of precursor delivered by this cycle can be estimated by assuming
that the vapor obeys the ideal gas law:
n=(P.sub.eq-P.sub.dep)(V/RT.sub.1) (14)
where R is the gas constant. This expression also assumes that
carrier gas from tube 90 does not enter chamber 60 through valve 70
during the brief time that it is open to release the precursor
vapor. If mixing of carrier gas with the precursor vapor does occur
during the time that valve 70 is open, then a larger dose of
precursor vapor may be delivered, up to a maximum value
n=(P.sub.eq)(V/RT.sub.1) (15)
if all the residual precursor vapor in chamber 60 is displaced by
carrier gas. For precursors with relatively high vapor pressure
(P.sub.eq>>P.sub.dep), there is not much difference between
these two estimates of the precursor dose.
[0085] This cycle of delivering precursor 20 is repeated if
necessary until the required dose of precursor 20 has been
delivered into reaction chamber. Normally, in an ALD process, the
dose of precursor 20 delivered by this cycle (or several such
cycles repeated to give a larger dose) is chosen to be large enough
to cause the surface reactions to go to completion (also called
"saturation").
[0086] Next a dose of vapor 31 from a second precursor 21 may be
measured and delivered by a similar apparatus with components
numbered similarly to the apparatus for the first precursor 20.
[0087] In the case of precursors with vapor pressure so low that
P.sub.eq is less than P.sub.dep, this method will not deliver any
precursor vapor into the deposition chamber. The vapor pressure can
be increased by raising the temperature T.sub.1, but in some cases
a higher temperature would result in thermal decomposition of the
precursor. In such cases of thermally sensitive precursors with low
vapor pressure, vapor may be delivered using the apparatus in FIG.
2. The chamber 220 is first pressurized with carrier gas delivered
through tube 240 and valve 200 from a pressure controller (not
shown). Valve 200 is then closed and valve 210 opened to allow the
carrier gas to pressurize precursor reservoir 220 to pressure
P.sub.tot. The mole fraction of precursor vapor in the vapor space
30 of reservoir 10 is then P.sub.eq/P.sub.tot. If P.sub.tot is set
to a pressure larger than the pressure P.sub.dep in the deposition
chamber, then the number of moles delivered in a dose can be
estimated from the equation
n=(P.sub.eq/P.sub.tot)(P.sub.tot-P.sub.dep)(V/RT.sub.1), (16)
where V is the volume of the vapor space 30 in chamber 10. This
dose is delivered by opening valve 230. Tf carrier gas from tube 90
enters the volume 30 during the time that the valve 230 is open,
then a dose somewhat larger than this estimate may be delivered. By
making the volume V large enough, a precursor dose that is
certainly large enough to saturate the surface reaction may be
delivered. If the vapor pressure P.sub.eq is so low that the
required volume V would be impracticably large, then additional
doses from volume V may be delivered before delivering a dose of
the other reactant.
[0088] A similar apparatus is provided for each precursor reactant
of the system. Thus, chamber 221 is first pressurized with carrier
gas delivered through tube 241 and valve 201 from a pressure
controller (not shown). Valve 201 is then closed and valve 211 is
opened to allow the carrier gas to pressurize precursor reservoir
11 to pressure P.sub.tot. This dose is delivered by opening valve
231. Carrier gas from tube 91 promotes transport of the metered
dose to the deposition chamber.
[0089] In an isothermal deposition zone, material is generally
deposited on all surfaces exposed to the precursor vapors,
including substrates and the interior chamber walls. Thus it is
appropriate to report the precursor doses used in terms of moles
per unit area of the substrates and exposed chamber walls.
[0090] The liquids and solutions described herein may also be used
as metal-containing precursors for other types of deposition
processes, such as spray coating, spin coating or sol-gel formation
of mixed metal oxides. The high solubility and miscibility of these
precursors is an advantage in forming the required solutions.
[0091] The amides disclosed in these examples appeared to be
non-pyrophoric by the methods published by the United States
Department of Transportation. One test calls for placing about 5
milliliters of the material on an non-flammable porous solid, and
observing that no spontaneous combustion occurs. Another test
involves dropping 0.5 milliliters of the liquid or solution on a
Whatman No. 3 filter paper, and observing that no flame or charring
of the paper occurs.
[0092] The precursors generally react with moisture in the ambient
air, and should be stored under an inert, dry atmosphere such as
pure nitrogen gas.
[0093] The invention may be understood with reference to the
following examples which are for the purpose of illustration only
and which are not limiting of the invention, the full scope of
which is set forth in the claims which follow.
Example 1
CVD of Zirconium Silicate
[0094] A solution (1% by weight) of tris(tert-butoxy)silanol in
mesitylene was pumped at a rate of 6 ml/hour into a 1/16'' O.D. tee
joint through which nitrogen gas flowed at 0.4 L/min. The resulting
fog flowed into a tube heated to 250.degree. C. A solution (1% by
weight) of tetrakis(ethylmethylamido)zirconium in mesitylene was
pumped at a rate of 12 ml/hour into another tee joint through which
nitrogen gas flowed at 0.4 L/min. The resulting fog flowed into the
same heated tube. The gas pressure was maintained at 5 Torr by a
vacuum pump attached to the outlet of the glass tube by a liquid
nitrogen trap. Substrates of silicon and glassy carbon placed
inside the tube were coated with a film of zirconium silicate whose
thickness varied along the length of the tube. Analysis of the film
by Rutherford backscattering spectroscopy gave a composition
ZrSi.sub.2O.sub.6 for films deposited on glassy carbon. No carbon
or nitrogen was detected in the film. The refractive indexes of
films deposited on silicon were found to be about 1.6 by
ellipsometry.
Example 2
ALD of Zirconium Silicate
[0095] Example 1 was repeated except that the precursors were
injected in alternate pulses spaced 5 seconds apart, instead of
continuously. A film of similar composition, ZrSi.sub.2O.sub.6, was
deposited with uniform thickness along the whole length of the
heated zone. The thickness was about 0.3 nm per cycle.
Example 3
CVD of Hafnium Silicate
[0096] Example 1 was repeated with
tetrakis(ethylmethylamido)hafnium in place of
tetrakis(ethylmethylamido)zirconium. Films of composition
approximately HfSi.sub.2O.sub.6 were formed. No carbon or nitrogen
was detected in the film. The refractive indexes of films deposited
on silicon were found to be about 1.6 by ellipsometry.
Example 4
ALD of Hafnium Silicate
[0097] Example 3 was repeated except that the precursors were
injected in alternate pulses spaced 5 seconds apart, instead of
continuously. A film of similar composition, HfSi.sub.2O.sub.6, was
deposited with uniform thickness along the whole length of the
heated zone. The thickness was about 0.3 nm per cycle.
Example 5
CVD of Yttrium Silicate
[0098] Example 1 was repeated with
tris(tert-butyl(trimethylsilyl)amido)yttrium in place of
tetrakis(ethylmethylamido)zirconium. Films of composition
approximately Y.sub.2Si.sub.2O.sub.7 were formed. No carbon or
nitrogen was detected in the film. The refractive indexes of films
deposited on silicon were found to be about 1.6 by
ellipsometry.
Example 6
ALD of Yttrium Silicate
[0099] Example 5 was repeated except that the precursors were
injected in alternate pulses spaced 5 seconds apart, instead of
continuously. A film of similar composition,
Y.sub.2Si.sub.2O.sub.7, was deposited with uniform thickness along
the whole length of the heated zone. The thickness was about 0.3 nm
per cycle. Composition approximately Y.sub.2Si.sub.2O.sub.7.
Example 7
CVD of Lanthanum Silicate
[0100] Example 1 was repeated with
tris(bis(trimethylsilyl)amido)lanthanum in place of
tetrakis(ethylmethylamido)zirconium and tetradecane in place of
mesitylene. Films with a La:Si ratio of about 0.9 were formed on a
glassy carbon substrate at a substrate temperature of 250.degree.
C. No carbon or nitrogen was detected in the films.
Example 8
ALD of Lanthanum Silicate
[0101] Example 7 was repeated except that the precursors were
injected in alternate pulses spaced 5 seconds apart, instead of
continuously. A film of similar composition was deposited with
uniform thickness along the whole length of the heated zone.
Example 9
CVD of Lithium Phosphate
[0102] Liquid lithium bis(ethyldimethylsilyl)amide (1 part by
weight) was mixed with mesitylene (99 parts). The resulting
solution was nebulized by pumping at a rate of 12 ml/hour into a
tee joint into nitrogen gas flowing at 0.30 L/min into the
deposition zone inside a tube (24 mm inside diameter) in a furnace
heated to 250.degree. C. Simultaneously a 1% mesitylene solution of
diisopropylphosphate was similarly nebulized into another nitrogen
carrier gas stream flowing at 0.30 L/min into the same tube
furnace. The gas pressure was maintained at 5 Torr by a vacuum pump
attached to the outlet of the glass tube by a liquid nitrogen trap.
A thin film was deposited on a silicon substrate placed on the
bottom of the glass tube, as well as on the inside of the tube. The
thickness profile showed a peak near the gas entrance to the tube
furnace. The film was analyzed by X-ray photoelectron spectroscopy
to contain lithium, phosphorus and oxygen.
Example 10
ALD of Lithium Phosphate
[0103] Example 9 was repeated with the change that the materials
were introduced in alternating pulses spaced 5 seconds apart in
time. A similar lithium phosphate film was deposited, except that
the thickness was nearly constant throughout the deposition
zone.
Comparative Example 1
Control Deposition with Only Tris(Tert-Butoxy)Silanol
[0104] Example 1 was repeated using only the silicon precursor and
no zirconium precursor. No film was deposited.
Comparative Example 2
Control Deposition with Only
Tetrakis(Ethylmethylamido)Zirconium
[0105] Example 1 was repeated using only the zirconium precursor
and no silicon precursor. No film was deposited.
Comparative Example 3
Control Deposition with Only Tetrakis(Ethylmethylamido)Hafnium
[0106] Example 3 was repeated using only the hafnium precursor and
no silicon precursor. No film was deposited.
Comparative Example 4
Control Deposition with Only
Tris(Tert-Butyl(Trimethylsilyl)Amido)Yttrium
[0107] Example 5 was repeated using only the yttrium precursor and
no silicon precursor. No film was deposited.
Comparative Example 5
Control Deposition with Only
Tris(Bis(Trimethylsilyl)Amido)Lanthanum
[0108] Example 7 was repeated using only the lanthanum precursor
and no silicon precursor. No film was deposited.
Comparative Example 6
Control Deposition with Only Diisopropylphosphate
[0109] Example 9 was repeated using only the phosphorus precursor
and no lithium precursor. No film was deposited.
Comparative Example 7
Control Deposition with Only Lithium
Bis(Ethyldimethylsilyl)Amide
[0110] Example 9 was repeated using only the lithium precursor and
no phosphorus precursor. No film was deposited.
Example 11
ADL Formation of Metal Silicates and Phosphates
[0111] The ALD examples 2, 4, 6, 8 and 10 were repeated using
automobile fuel injectors (Ford model CM-4722 F13Z-9F593-A) to
deliver pulses of the solutions of precursors into the nitrogen
carrier gas. About 0.05 m of solution was delivered each time that
a valve was opened for about 50 milliseconds. Similar results were
obtained.
[0112] The ALD examples 2, 4, 6, 8 and 10 were repeated using a
6-port sampling valves (Valco model EP4C6WEPH, Valco Instruments,
Houston, Tex.) normally used for injecting samples into gas
chromatographs to deliver pulses of tetradecane solutions into the
nitrogen carrier gas. External sample loops having volumes of 50
microliters were used. Each time that a valve was opened, about 50
microliters of solution flowed into a 1/16'' O. D., 0.040'' I. D.
nickel tube in which the solution was vaporized by heat from hot
oil flowing over the outside of the tube. Nitrogen carrier gas
moved the vapor from the small tube into the ALD reactor tube.
Similar results were obtained.
[0113] In another series of examples, pulses of those precursors
that are liquids at room temperature were delivered for ALD
experiments similar to examples 2, 4, 6, 8 and 10 using 4-port
sampling valves with small (0.5 microliter) internal sampling loops
(Valco model EH2CI4WE.5PH, Valco Instruments, Houston, Tex.). Each
time that a valve was opened, about 0.5 microliters of liquid
flowed into a 1/16'' O. D., 0.040'' I. D. nickel tube in which the
liquid was vaporized by heat from hot oil flowing over the outside
of the tube. Nitrogen carrier gas moved the vapor from the small
tube into the ALD reactor tube. Similar results were obtained.
Example 12
ALD of Hafnium Oxide
[0114] A hafnium oxide layer was deposited using the apparatus of
FIG. 1. Doses of 0.5.times.10.sup.-9 moles/cm.sup.2 of
tetrakis(dimethylamido)hafnium vapor and 4.times.10.sup.-9
moles/cm.sup.2 of water vapor were injected alternately every 5
seconds into a deposition chamber held at 250.degree. C. The
chamber was also fed a continuous flow of nitrogen carrier gas
sufficient to maintain a pressure of 0.15 Torr. The deposition
chamber had a cross-sectional area of 2.3 square centimeters in the
plane perpendicular to the direction of gas flow through the
chamber. The outlet of the deposition chamber was attached to a
vacuum pump with capacity (195 liters/minute) sufficient to pump a
volume equal to the deposition chamber in about 0.012 seconds.
[0115] As a result of these reaction conditions, a transparent,
electrically insulating hafnium oxide film was deposited on
substrates in the deposition chamber and onto its inner walls. Its
composition was determined to be HfO.sub.2 by Rutherford
backscattering spectroscopy (RBS) of a film on a glassy carbon
substrate. No carbon or nitrogen was detected (<1 atomic
percent). By ellipsometry, its thickness was determined to be 0.1
nanometer/cycle and its refractive index 2.05. Combining data from
RBS and ellipsometry yielded a density of about 9. The thickness
was constant over the whole deposition region, to within the
estimated measurement error of about 1%. Small-angle X-ray
reflectivity measurements confirmed the thickness and gave a
density of 9.23 g/cm.sup.3. X-ray reflectivity also showed that the
films are very smooth, with root mean square surface roughness
about 0.4 nm for a film 43 nm thick. Scanning electron microscopy
showed that films grown at 150.degree. C. are even smoother than
the ones grown at 250.degree. C.
[0116] Repeating Example 12 with higher doses of either reactant
did not increase the film thickness or change its properties. These
results show that the surface reactions are self-limiting. This
conclusion was confirmed by placing inside the deposition chamber
110 a quartz crystal micro-balance (not shown), which showed that
the amount of mass deposited first increased and then reached a
plateau as the size of each dose was increased. As a result of
these self-limiting surface reactions, uniform films could be
deposited inside holes with ratios of length to diameter over 50.
Uniformity of thickness inside these holes was improved by
increasing the dose to 10 times the minimum required for saturation
of the reactions on a flat surface without the holes. Reducing the
capacity (speed) of the vacuum pump also helps to improve the step
coverage by reducing the linear velocity of the vapors through the
deposition chamber, thereby increasing the time during which the
vapors can diffuse down the holes, i.e. increasing the flux
(Langmuirs of exposure). FIG. 3 shows a scanning micrograph of
holes coated with hafnium oxide, cleaved to reveal their highly
uniform thickness. The hafnium oxide layer is the bright line
outlining each of the narrow vertical holes in the silicon, which
appears as a dark background. At the top of the micrograph is the
upper surface of the silicon from which the holes were etched prior
to the deposition of the hafnium oxide.
[0117] Repeating Example 12 with substrate temperatures in the
range from 100.degree. C. to 300.degree. C. gave similar results.
At temperatures above 300.degree. C., the thickness increased with
increasing the dose of tetrakis(dimethylamido)hafnium. This shows
that the surface reaction is not self-limiting at temperatures
above 300.degree. C., due to thermal decomposition of
tetrakis(dimethylamido)hafnium.
Example 13
ALD of Zirconium Oxide
[0118] Example 12 was repeated with
tetrakis(dimethylamido)zirconium in place of
tetrakis(dimethylamido)hafnium. Films of zirconium dioxide with
similar properties were deposited.
Example 14
ALD of Hafnium Oxide
[0119] Example 12 was repeated with tert-butmol vapor in place of
water vapor. Films of hafnium dioxide with similar properties were
deposited.
Example 15
ALD of Tantalum Oxide
[0120] Example 12 was repeated with
ethylimidotris(diethylamido)tantalum vapor in place of
tetrakis(dimethylamido)hafnium vapor. Transparent films of
Ta.sub.2O.sub.5 were deposited. They have a refractive index of
2.2, and a thickness of about 0.06 nm per cycle.
Example 16
ALD of Aluminum Phosphate
[0121] ALD was carried out using alternating doses of
3.times.H).sup.-9 moles/cm.sup.2 of the vapors of trimethylaluminum
and diisopropylphosphate at a substrate temperature of 400.degree.
C. Transparent aluminum phosphate films with approximate
composition A.sub.12P.sub.4O.sub.13 were deposited at a rate of 0.1
nm per cycle. They had a refractive index of about 1.5.
Example 17
ALD of Aluminum Silicate
[0122] ALD was carried out using alternating doses of
3.times.10.sup.-9 moles/cm.sup.2 of trimethylaluminum vapor and
1.2.times.10.sup.-8 moles/cm.sup.2 of tris(tert-butoxy)silanol
vapor at a substrate temperature of 300.degree. C. Transparent
aluminum silicate films with approximate composition
Al.sub.2Si.sub.8O.sub.19 were deposited at a remarkably high rate
of 1 nm per cycle. They had a refractive index of about 1.48. The
surfaces of the films are very smooth; atomic force microscopy
determined a root mean square roughness of less than 0.8 nm for an
aluminum silicate film 150 nm thick. The tensile stress in a film 2
micrometers thick on a silica substrate was measured to be about
0.2 giga-Pascals. A similar film deposited on single-crystalline
silicon showed a smaller tensile stress of 0.03 giga-Pascals. A
film 6 microns thick showed cracks and delamination because of the
tensile stress.
[0123] This tensile stress can be reduced, eliminated, or even
reversed to compressive stress by plasma treatment. The deposition
is temporarily halted after a thin layer (such as 5 to 10 nm) has
been deposited, a radio-frequency plasma (in a low-pressure gas
such as O.sub.2+argon) is applied, and then the plasma power is
stopped and the deposition is resumed. Multiple cycles of
deposition and plasma treatment may be used to build up thicker
layers with tensile or compressive stress values adjusted to the
requirements of particular applications, particularly those
requiring thicker films.
Example 18
ALD of Aluminum Silicate
[0124] ALD was carried out using alternating doses of
3.times.10.sup.-9 moles/cm.sup.2 of trimethylaluminum vapor and
3.times.10.sup.-8 moles/cm.sup.2 of tris(tert-butoxy)silanol vapor
at a substrate temperature 200.degree. C. Transparent aluminum
silicate films with approximate composition
Al.sub.2Si.sub.16O.sub.35 were deposited at a remarkably high rate
of 2 nm per cycle. They had a refractive index of about 1.47.
Example 19
ALD of Aluminum Silicate
[0125] ALD was carried out with alternating doses of
3.times.10.sup.-9 moles/cm.sup.2 of tris(dimethylamino)aluminum
vapor and 3.times.10.sup.-8 moles/cm.sup.2 of
tris(tert-butoxy)silanol vapor at a substrate temperature
250.degree. C. An aluminum silicate film was formed with thickness
0.1 nm/cycle and a refractive index of about 1.46.
Example 20
ALD of Aluminum Silicate
[0126] Example 19 was repeated with tris(tert-pentyloxy)silanol
vapor in place of the tris(tert-butoxy)silanol vapor. Similar
results were obtained.
Example 21
ALP of Aluminum Silicate
[0127] Example 19 was repeated with a dose of water vapor between
the doses of tris(dimethylamino)aluminum vapor and
tris(tert-butoxy)silanol vapor. A similar film was obtained with
very uniform thickness of 0.1 nm/cycle (.+-.1%) along the direction
of gas flow.
Example 22
ALD of Lanthanum Silicate
[0128] Example 12 was repeated with
tris(bis(trimethylsilyl)amido)lanthanum vapor in place of
tetrakis(dimethylamido)hafnium vapor and with the apparatus of FIG.
2, used as described herein above. Transparent oxide films with a
La:Si ratio of about 2 were formed on substrates at a substrate
temperature of 250.degree. C. No carbon or nitrogen was detected in
the films. They have a refractive index of 1.7, and a thickness of
about 0.1 nm per cycle.
Example 23
ALD of Lanthanum Oxide
[0129] ALD can be carried out with alternating doses of
tris(2,2,6,6-tetramethylpiperidido)lanthanum vapor using the
apparatus of FIG. 2 and water vapor to form lanthanum oxide
films.
Example 24
ALD of Silicon Dioxide
[0130] ALD can be carried out with alternating doses of
tetraisocyanatosilane vapor and tris(tot-butoxy)silanol vapor to
form silicon dioxide films. Larger fluxes of exposure
(>10.sup.-7 Langmuirs) are required for these less reactive
precursors.
[0131] Those skilled in the art will recognize or be able to
ascertain using no more than routine experimentation, many
equivalents to the specific embodiments of the invention described
specifically herein. Such equivalents are intended to be
encompassed in the scope of the following claims.
* * * * *