U.S. patent application number 11/008069 was filed with the patent office on 2006-06-15 for precursors for silica or metal silicate films.
Invention is credited to Xinjian Lei, Ron Rulkens.
Application Number | 20060127578 11/008069 |
Document ID | / |
Family ID | 35871081 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127578 |
Kind Code |
A1 |
Lei; Xinjian ; et
al. |
June 15, 2006 |
PRECURSORS FOR SILICA OR METAL SILICATE FILMS
Abstract
A composition selected from the group consisting of
bis(tert-butoxy)(isopropoxy)silanol,
bis(isopropoxy)(tert-butoxy)silanol,
bis(tert-pentoxy)(isopropoxy)silanol,
bis(isopropoxy)(tert-pentoxy)silanol,
bis(tert-pentoxy)(tert-butoxy)silanol,
bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof; its use
to form a metal or metalloid silicate layer on a substrate and the
synthesis of the mixed alkoxysilanols.
Inventors: |
Lei; Xinjian; (Vista,
CA) ; Rulkens; Ron; (Milpitas, CA) |
Correspondence
Address: |
AIR PRODUCTS AND CHEMICALS, INC.;PATENT DEPARTMENT
7201 HAMILTON BOULEVARD
ALLENTOWN
PA
181951501
US
|
Family ID: |
35871081 |
Appl. No.: |
11/008069 |
Filed: |
December 9, 2004 |
Current U.S.
Class: |
427/255.31 ;
556/10; 556/457 |
Current CPC
Class: |
C23C 16/40 20130101;
C07F 7/04 20130101 |
Class at
Publication: |
427/255.31 ;
556/010; 556/457 |
International
Class: |
C07F 7/08 20060101
C07F007/08; C23C 16/00 20060101 C23C016/00; C23C 16/06 20060101
C23C016/06; B05D 3/02 20060101 B05D003/02 |
Claims
1. A composition selected from the group consisting of
bis(tert-butoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-butoxy)silanol,
bis(tert-pentoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-pentoxy)silanol,
bis(tert-pentoxy)(tert-butoxy)silanol,
bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof.
2. The invention of claim 1 wherein the composition is
bis(iso-propoxy)(tert-butoxy)silanol.
3. The invention of claim 1 wherein the composition is
bis(tert-pentoxy)(iso-propoxy)silanol.
4. The invention of claim 1 wherein the composition is
bis(iso-propoxy)(tert-pentoxy)silanol.
5. The invention of claim 1 wherein the composition is
bis(tert-pentoxy)(tert-butoxy)silanol.
6. The invention of claim 1 wherein the composition is
bis(tert-butoxy)(tert-pentoxy)silanol.
7. Bis(tert-butoxy)(iso-propoxy)silanol.
8. A method for forming a metal or metalloid silicate on a
substrate, comprising contacting a metal or metalloid containing
compound with a mixed alkoxysilanol selected from the group
consisting of bis(tert-butoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-butoxy)silanol,
bis(tert-pentoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-pentoxy)silanol,
bis(tert-pentoxy)(tert-butoxy)silanol,
bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof and
reacting the metal or metalloid containing compound with the mixed
alkoxysilanol to form the metal or metalloid silicate on the
substrate.
9. The method of claim 8 wherein the metal or metalloid containing
compound is in the vapor state during reaction.
10. The method of claim 8 wherein the mixed alkoxysilanol is in the
vapor state during reaction.
11. The method of claim 8 wherein the mixed alkoxysilanol is
bis(tert-butoxy)(iso-propoxy)silanol.
12. The method of claim 8 wherein the metal or metalloid is
selected from the group consisting of titanium, hafnium, zirconium,
yttrium, lanthanum, scandium magnesium, boron, aluminum and
mixtures thereof.
13. The method of claim 12 wherein the metal or metalloid
containing compound is selected from metal amides, metal alkoxides,
metal hydrides, metal alkyls and mixtures thereof
14. A method for forming a metal or metalloid silicate on a
substrate, comprising contacting a metal or metalloid containing
compound with bis(tert-butoxy)(iso-propoxy)silanol and reacting the
metal or metalloid containing compound with the
bis(tert-butoxy)(iso-propoxy)silanol to form the metal or metalloid
silicate on the substrate.
15. A method of synthesizing a mixed alkoxysilanol, comprising;
reacting silicon tetrachloride with a first alkanol or its metal
salt to form an alkoxychlorosilane and further reacting the
alkoxychlorosilane with a second alkanol or its metal salt, where
the first alkanol is different than the second alkanol, to form a
mixed alkoxysilanol.
16. The method of claim 14 wherein the first alkanol is
tert-butanol and the second alkanol is iso-propanol.
17. The method of claim 14 wherein the first alkanol is
tert-pentanol and the second alkanol is iso-propanol.
Description
BACKGROUND OF THE INVENTION
[0001] Alkoxysilanols are attaining increased attention in the
fabrication of electronic devices, where they are reacted with
metal containing precursors to deposit films of silicon and metal
containing materials. Specifically, as component device (i.e.,
transistors) size shrinks and increasing densities of component
devices and circuits are patterned, traditional silica dielectric
insulating materials between those component devices and circuits
are inadequate and the industry has sought better dielectric
materials deposited at relatively low temperature. Alkoxysilanols
reacted with metal containing compounds at temperature below
300.degree. C. have been investigated to achieve the needed low
dielectric insulating materials to electrically isolate smaller
electronic component devices and circuits having increased
densities and smaller overall dimensions.
[0002] WO 02/27063 describes alkoxysilanols, such as
tris-(tert-butoxy)silanol, for reaction with metals or metalloid
containing precursors to deposit metal or metalloid silicate. The
alkoxysilanols are generically described as containing:
[(R.sup.1)(R.sup.2)(R.sup.3)CO]--[(R.sup.4)(R.sup.5)(R.sup.6)CO]--[(R.sup-
.7)(R.sup.8)(R.sup.9)CO]--SiOH; where R.sup.n can be the same or
different, n=1-9.
[0003] WO 03/083167 also describes alkoxysilanols of the same scope
described in WO 02/270063 for reaction with aluminum containing
precursors to form silica aluminates.
[0004] Backer, et. al., "Esters Mixtes De L'Acide
Tetrathio-Orthosilicique", Rec. Trav. Chim., 61, (1942), pp
500-512, describes the synthesis of tris-(butoxy)silanol.
[0005] Goedel, et. al., "Hyperbranched Poly(alkoxysilonanes)",
Polymer Preprints, 42(1), (2001), pp 242-243, discloses the
polymerization of alkoxysilanols, such as tris-(ethoxy)silanol.
[0006] Hausman, et. al., "Rapid Vapor Deposition of Highly
Conformal Silica Nanoaluminates", Science, Vol. 298, Oct. 11, 2002,
pp 402-406, describes the atomic layer deposition (ALD) of
tris-(tert-butoxy)silanol and trimethylaluminum in alternating
sequence to provide thin films, which can be used in electronic
applications.
[0007] Muller, Richard, "Zur Darstellung von Alkoxy- und
Alkoxysiloxy-silanolen", Z. Chem., 23, J g. (1983), p 252,
identifies various tris-(alkoxy) silanols in its Table 1, last
entry, and Table 2, including in the latter; tris-(PhO)silanol.
[0008] Schott, et. al., "Alkoxy-silanole--partielle
Kieselsaureester", Z. Anorg. Allg. Chemie, 459, (1979), pp 177-186,
discloses the synthesis of trialkoxy silanoles and dialkoxy
silandioles.
[0009] Alkoxysilanols that have been presently contemplated for
manufacturing silica-metal films have suffered from undesirable
physical properties. To facilitate ease of use, alkoxysilanols
should be readily synthesized, available in high purity and exhibit
ease of delivery from the site of storage to the site of reaction.
The novel alkoxysilanols of the present invention overcome the
disadvantages of the prior art and exhibit good properties for
manufacturing silica-metal films, as will be demonstrated
below.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention is a composition selected from the
group consisting of bis(tert-butoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-butoxy)silanol,
bis(tert-pentoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-pentoxy)silanol,
bis(tert-pentoxy)(tert-butoxy)silanol,
bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof; its use
to form a metal or metalloid silicate layer on a substrate and the
synthesis of the mixed alkoxysilanols.
BRIEF DESCRIPTION OF THE DRAWING
[0011] The drawing is a graph of a comparison of the vapor pressure
of the prior art alkoxysilanol; tris(tert-pentoxy)silanol (TPOSL)
versus the novel mixed alkoxysilanol;
bis(tert-butoxy)(isopropoxy)silanol (BTBIPOSL) showing a consistent
10-fold higher vapor pressure for the
bis(tert-butoxy)(isopropoxy)silanol over a range of preferred
potential operating temperatures for the film deposition process in
which the alkoxysilanols would be used.
DETAILED DESCRIPTION OF THE INVENTION
[0012] This invention is related to a novel class of mixed
alkoxysilanols, their synthesis and use. These mixed alkoxysilanols
can be employed as potential precursors to make silica or metal
silicates via either the chemical vapor deposition (CVD) or atomic
layer deposition (ALD) method at temperatures less than 500.degree.
C. These compounds are prepared via reaction of SiCl.sub.4 with two
equivalents of either bulky alcohols (HOR.sup.1), such as
tert-butanol or tert-pentanol, in the presence of base or metal
alkoxides (MOR.sup.1, i.e., metal salt of the alcohol), followed by
addition of one equivalent of either less bulky alcohol
(HOR.sup.2), such as iso-propanol, in the presence of base or the
corresponding metal alkoxide (MOR.sup.2), then followed by
hydrolysis at lower temperature.
[0013] The mixed alkoxysilanols are found to be liquid at room
temperature and thermally stable. Being liquid and having higher
vapor pressure, these new compounds are better precursors, than
those commercially available tris(alkoxy)silanols, such as;
tris(tert-butoxy)silanol (TBOSL) or tris(tert-pentoxy)silanol
(TPOSL), since TBOSL is a solid at room termperature and TPOSL's
vapor pressure is very low (.about.2 torr at 96.degree. C.).
[0014] These novel, thermally stable, mixed alkoxysilanols have
been prepared as potential precursors for forming low thermal
budged metal silicates or silica films. Among the mixed
alkoxysilanols, bis(tert-butoxy)(iso-propoxy)silanol is easy to
prepare and is possible to make in the high purity required by the
semiconductor industry. The vapor pressure of
bis(tert-butoxy)(iso-propoxy)silanol was found to be about 10 times
higher (see the drawing), than that of tris(tert-pentoxy)silanol
(TPOSL), a precursor currently evaluated by the semiconductor
industry as a potential source for ALD SiO.sub.2, thus making the
mixed alkoxysilanols better precursors as CVD or ALD
precursors.
[0015] Tris(alkoxy)silanol precursors are commercially available.
They can be prepared via a two-step procedure, i.e. either equation
1 or equation 2, followed by hydrolysis, as in equation 3.
SiCl.sub.4+3ROH.fwdarw.(RO).sub.3SiCl+3HCl 1
SiCl.sub.4+3MOR.fwdarw.(RO).sub.3SiCl+3MCl (M=Li, K, Na) 2
(RO).sub.3SiCl+H.sub.2O.fwdarw.(RO).sub.3SiOH+HCl 3
[0016] The thermal stability of the tris(alkoxy)silanol is directly
related to the alkyl groups. For example, tris(tert-butoxy)silanol
and tris(tert-pentoxy)silanol are very stable, whereas
tris(iso-propoxy)silanol and tris(ethoxy)silanol are not stable and
undergo polymerization to form polysiloxanes upon heating.
[0017] The synthesis of mixed alkoxysilanol is more complicated,
involving a three-step process as shown in equations 4 to 7.
SiCl.sub.4+nR.sup.1OH.fwdarw.(R.sup.1O).sub.nSiCl.sub.4-n+nHCl 4
SiCl.sub.4+nMOR.sup.1.fwdarw.(R.sup.1O).sub.nSiCl.sub.4-n+nMCl 5
(R.sup.1O).sub.nSiCl.sub.4-n+mR.sup.2OH.fwdarw.(R.sup.1O).sub.n(R.sup.2O)-
.sub.mSiCl+mHCl 6
(R.sup.1O).sub.n(R.sup.2O).sub.mSiCl+H.sub.2O.fwdarw.(R.sup.1O).sub.n(R.s-
up.2O).sub.mSiOH+HCl 7
[0018] where n=1-2; m=1-2 and n+m=3.
[0019] In order to make stable mixed alkoxysilanol, it is preferred
to choose a bulky alcohol for the first step (equation 4 or 5) to
prevent further substitution of chloro ligands, allowing
quantitative conversion of SiCl.sub.4 into
monoalkoxytrichlorosilane or bis(alkoxy)dichlorosilane. If the
alkoxy groups are not bulky enough, a mixture of
alkoxytrichlorosilane, bis(alkoxy)dichlorosilane and
tris(alkoxy)chlorosilane would be generated. Thus, tert-butanol or
tert-pentanol is preferred for the first step. Preferably two
equivalents of bulky alcohol are used to make
bis(alkoxy)dichlorosilane. The distinct alcohol for the second step
should also be bulky enough to prevent formation of fully
substituted alkoxysilane, but only one equivalent of the second
alcohol should be used to avoid full substitution of the
silanol.
[0020] For example, if two-equivalents of tert-butanol is used in
the first step and two equivalents of iso-propanol is employed in
the second step, then the undesired
bis(tert-butoxy)bis(iso-propoxy)silane is formed. The resulting
fully substituted alkoxysilane would be extremely difficult to
remove from the final product, mixed alkoxysilanol, as their
boiling points are usually too close.
[0021] The by-product HCl plays a role in the stability of the
resulting mixed alkoxysilanols. There are two ways to remove the
generated HCl from the reaction: as organic base salt, such as
pyridine. HCl; or as inorganic base. Inorganic base is preferable
over organic base, since the organic base can cause problems in the
following separation or CVD/ALD process. Reaction temperature is
also important in successful synthesis of mixed alkoxysilanols, as
higher temperature promotes other reactions, which result in
products that will be difficult to separate out later by
distillation.
[0022] The following examples demonstrate that it is possible to
obtain the desirable mixed alkoxysilanols. The actual large scale
process to make these compounds can be varied depending on the
compound itself.
EXAMPLE 1
Synthesis of bis(iso-propoxy)(tert-pentoxy)silanol
[0023] 20 g (0.118 mol) of SiCl.sub.4 was loaded in a 1000 ml
three-neck flask with 500 ml hexanes. The flask was cooled down to
-40.degree. C. with a cold bath containing dry ice and
iso-propanol. 18 ml (0.237 mol) of iso-propanol and 11.3 ml (0.118
mol) of tert-pentanol were added slowly via addition funnel. The
temperature was kept at less than -20.degree. C. 30 ml of pyridine
was added to the flask slow to generate a lot of white precipitate
which is pyridine.HCl. The cold bath was removed and the flask was
stirred for 3 hours. Gas chromatograph/mass spectrometer (GC/MS)
measurement of the reaction mixture indicated formation of
bis(iso-propoxy)(tert-pentoxy)chlorosilane, plus other products.
Filtration and removal of solvents resulted in about 23 g of white
slurry. The white slurry was dropwise added to a solution
containing 40 ml of ether, 15 ml of water, and 15 ml of pyridine at
a temperatue below -20.degree. C. until completion of the addition.
The resulting white slurry was stirred for 3 hours. The organic
layer was separated and dried over anhydrous CaCl.sub.2 for two
days. GC/MS indicated formation of
bis(iso-propoxy)(tert-pentoxy)silanol (79.5%) as the major product,
plus tetrakis(iso-propoxy)silane (2.8%),
tris(iso-propoxy)(tert-pentoxy)silane (12.4%), and
tris(iso-propoxy)silanol (1.3%). It was very difficult to separate
bis(iso-propoxy)(tert-pentoxy)silanol from
tris(sio-propoxy)(tert-pentoxy)silane via vacuum distillation.
However, it would be possible to purify it if the synthesis was
done on a large scale.
EXAMPLE 2
Synthesis of bis(iso-propoxy)(tert-butoxy)silanol
[0024] 20 g (0.118 mol) of SiCl.sub.4 was loaded in a 1000 ml
three-neck flask with 500 ml hexane. The flask was cooled down to
-40.degree. C. with a cold bath containing dry ice and
iso-propanol. 11.3 ml (0.118 mol) of tert-butanol was added slowly
via addition funnel. The temperature was kept at less than
-20.degree. C. 10 ml of pyridine was added to the flask slowly to
generate a lot of white precipitate, which is pyridine.HCl. The
cold bath was removed and the flask was stirred for 3 hours. A
mixture of 18 ml iso-propanol and 20 ml pyridine were added slowly
to the resulting white slurry. The reaction mixture was stirred
overnight. GC/MS measurement of the reaction mixture indicated
formation of bis(iso-propoxy)(tert-butoxy)chlorosilane and
tris(iso-propoxy)(tert-butoxy)silane. Filtration and removal of
solvents resulted in white slurry. The white slurry was dropwise
added to a solution containing 50 ml of ether, 50 ml of water, and
15 ml of pyridine at temperatue below -20.degree. C. until
completion of the addition. The resulting white slurry was stirred
for 2 hours. The organic layer was separated and dried over
anhydrous CaCl.sub.2 for two days. GC/MS indicated formation of
bis(iso-propoxy)(tert-butoxy)silanol as the major product (55%),
plus tris(sio-propoxy)(tert-butoxy)silane (34%).
EXAMPLE 3
Synthesis of bis(tert-butoxy)(iso-propoxy)silanol
[0025] 20 g (0.118 mol) of SiCl.sub.4 was loaded in a 1000 ml
three-neck flask with 400 ml hexane. The flask was cooled down to
-40.degree. C. with a cold bath containing dry ice and
iso-propanol. 22.6 ml (0.236 mol) of tert-butanol was added slowly
via addition funnel. The temperature was kept at less than
-20.degree. C. 20 ml of pyridine was added to the flask slowly to
generate a lot of white precipitate, which is pyridine.HCl. The
cold bath was removed and the flask was stirred overnight after
removal of the cold bath. Filtration was applied to give a liquid
to which 9 ml (0.118 mol) of iso-propanol was added at temperature
below 40.degree. C. 10 ml of pyridine was added slowly to the
resulting white slurry. The reaction mixture was stirred for 5
hours after removal of the cold bath. Filtration and removal of
solvents resulted in white slurry. The white slurry was dropwise
added to a solution containing 50 ml of ether, 50 ml of water, and
15 ml of pyridine at temperatue below -0.degree. C. until
completion of the addition. The resulting white slurry was stirred
overnight. The organic layer was separated and dried over anhydrous
CaCl.sub.2 for several days. GC/MS indicated formation of
bis(tert-butoxy)(iso-propoxy)silanol as the major product
(>80%), plus bis(iso-propoxy)bis(tert-butoxy)silane. Vacuum
distillation gave pure bis(tert-butoxy)(iso-propoxy)silanol
(.about.104.degree. C./2 torr). Thermogravimetric
analysis/differential scanning calorimetry (TGA/DSC) measurement
shows the boiling point is 207.degree. C.
EXAMPLE 4
Synthesis of bis(tert-butoxy)(iso-propoxy)silanol
[0026] 20 g (0.0799 mol) of bis(tert-butoxy)dichlorosilane prepared
by reaction of SiCl.sub.4 with two equivalents of tert-butanol in
the presence of pyridine was loaded in a 1000 ml three-neck flask
with 200 ml hexane. The flask was cooled down to -20.degree. C.
with a cold bath containing dry ice and iso-propanol. 4.8 g (0.08
mol) of iso-propanol was added. The temperature was kept at less
than -20.degree. C. 6.3 g of pyridine was added to the flask slowly
to generate a lot of white precipitate, which is pyridine.HCl. The
cold bath was removed and the flask was stirred for several days at
room temperature after removal of the cold bath. Filtration and
removal of solvents resulted in white slurry. The white slurry was
dropwise added to a solution containing 50 ml of ether, 50 ml of
water, and 6 g of NH.sub.4.HCO.sub.3 at a temperatue below
-10.degree. C. until completion of the addition. The resulting
white slurry was stirred overnight. The organic layer was separated
and dried over anhydrous CaCl.sub.2. GC/MS indicated the formation
of bis(tert-butoxy)(iso-propoxy)silanol as the major product
(93.8%), plus bis(tert-butoxy)(iso-propoxy)chlorosilane. Vacuum
distillation gives pure bis(tert-butoxy)(iso-propoxy)silanol
(.about.104.degree. C./2 torr).
[0027] Being liquid and having higher vapor pressure, these new
mixed alkoxysilanols are better precursors than those commercially
available tris(alkoxy)silanols, such as; tris(tert-butoxy)silanol
(TBOSL) or tris(tert-pentoxy)silanol (TPOSL), since TBOSL is a
solid at room termperature and TPOSL's vapor pressure is very low
(.about.2torr at 96 C).
[0028] The novel mixed alkoxysilanols may be used advantageously in
a method for forming a metal or metalloid silicate on a substrate,
such as a dielectric layer in an electronic device fabrication of
solid state transistors, capacitors, vias, and circuits in general
by contacting a metal or metalloid containing compound with a mixed
alkoxysilanol selected from the group consisting of
bis(tert-butoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-butoxy)silanol,
bis(tert-pentoxy)(iso-propoxy)silanol,
bis(iso-propoxy)(tert-pentoxy)silanol,
bis(tert-pentoxy)(tert-butoxy)silanol,
bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof and
reacting the metal or metalloid containing compound with the mixed
alkoxysilanol to form the metal or metalloid silicate on the
substrate. Preferably, the mixed alkoxysilanols and the metal or
metalloid containing compounds are each made available in the
liquid state to ease transport to the reaction chamber or tool
where they are blended and reacted, and they are both preferably
vaporized in that reaction chamber or tool at low temperatures to
maintain the thermal budget of the electronic device being
fabricated. Typically, the metal or metalloid is selected from the
group consisting of titanium, hafnium, zirconium, yttrium,
lanthanum, scandium, magnesium, boron, aluminum and mixtures
thereof. The ligand which is used to make the metal or metalloid
compound could be amides, alkyls, alkoxides, halides and mixtures
thereof.
[0029] The present invention has been described with regard to
several preferred embodiments, however, the full scope of the
present invention should be ascertained from the claims which
follow.
* * * * *