U.S. patent application number 11/451596 was filed with the patent office on 2006-12-28 for organo functionalized silane monomers and siloxane polymers of the same.
Invention is credited to Jyri Paulasaari, Jarkko Pietikainen, Juha T. Rantala.
Application Number | 20060293482 11/451596 |
Document ID | / |
Family ID | 37025000 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060293482 |
Kind Code |
A1 |
Rantala; Juha T. ; et
al. |
December 28, 2006 |
Organo functionalized silane monomers and siloxane polymers of the
same
Abstract
A thin film comprising a composition obtained by polymerizing a
monomer having the formula I: ##STR1## wherein: R.sub.1 is a
hydrolysable group, R.sub.2 is an organic crosslinking group, a
reactive cleaving group or a polarizability reducing organic group,
and R.sub.3 is a bridging linear or branched bivalent hydrocarbyl
group to form a siloxane material. The organo-functionalized
molecule is capable of further reacting in the matrix so as to
undergo cross-linking, cleaving or combination of both. The present
invention provides excellent chemical resistance and very low
chemical adsorption behavior due to high cross-linking bridging
group density.
Inventors: |
Rantala; Juha T.; (Espoo,
FI) ; Paulasaari; Jyri; (Turku, FI) ;
Pietikainen; Jarkko; (Helsinki, FI) |
Correspondence
Address: |
KUBOVCIK & KUBOVCIK
SUITE 710
900 17TH STREET NW
WASHINGTON
DC
20006
US
|
Family ID: |
37025000 |
Appl. No.: |
11/451596 |
Filed: |
June 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60689541 |
Jun 13, 2005 |
|
|
|
Current U.S.
Class: |
528/35 |
Current CPC
Class: |
C09D 183/04 20130101;
H01L 21/02282 20130101; H01L 21/02126 20130101; H01L 21/3127
20130101; C08G 77/50 20130101; H01B 3/46 20130101; H01L 21/02216
20130101; H01L 21/3122 20130101; Y10T 428/31663 20150401; C08G
77/08 20130101; C09D 183/14 20130101 |
Class at
Publication: |
528/035 |
International
Class: |
C08G 77/60 20060101
C08G077/60 |
Claims
1. A thin film comprising a composition obtained by polymerizing a
monomer having the formula I: ##STR17## wherein: R.sub.1 is a
hydrolysable group, R.sub.2 is an organic crosslinking group, a
reactive cleaving group or a polarizability reducing organic group,
and R.sub.3 is a bridging linear or branched bivalent hydrocarbyl
group. to form a siloxane material.
2. The thin film according to claim 1, wherein independently
R.sub.1 is selected from the group of hydrogen, halides, alkoxy and
acyloxy groups, R.sub.2 is selected from alkyl groups, alkenyl
groups and aryl groups, and R.sub.3 is selected from linear and
branched alkylene groups, alkenylene groups, alkynylene groups,
bivalent alicyclic groups, bivalent polycyclic groups, and bivalent
aromatic groups.
3. The thin film according to claim 1, wherein the composition
comprises a cross-linked poly(organosiloxane).
4. The thin film according to any of claims 1 to 3, wherein the
composition is obtained essentially by homopolymerization of
monomers having formula I.
5. The thin film according to any of claims 1 to 3, wherein the
composition is obtained by copolymerizing first monomers having
formula I, wherein R.sub.3 stands for a linear bivalent hydrocarbyl
residue, with second monomers having formula I, wherein R.sub.3
stands for a branched bivalent hydrocarbyl residue, the molar ratio
of the first monomers to the second monomers is 95:5 to 5:95, in
particular 90:10 to 10:90, preferably 80:20 to 20:80.
6. The thin film according to any of the preceding claims,
comprising a cured thin layer of the poly(organosiloxane) having a
thickness of 0.01 to 50 um, in particular 0.5 to 5 um, preferably
from 1 to 3 un.
7. The thin film according to any of the preceding claims, having a
density of at least 1.2 g/cm.sup.3, preferably 1.45 g/cm.sup.3 or
more, more preferably 1.60 g/cm.sup.3 or more, in particular up to
about 2.5 g/cm.sup.3.
8. The thin film according to any of the preceding claims, having
either or both of the following properties: a glass transition
temperature, which is higher than 200.degree. C., in particular
400.degree. C. or more, in particular 500.degree. C. or more, and a
dielectric constant of 3.0 or less, in particular 2.9 or less,
preferably about 2.5 to 1.9.
9. The thin film according to any of the preceding claims, having a
coefficient of thermal expansion of 12-22 ppm, preferably about
15-20 ppm.
10. The thin film according to any of the preceding claims,
comprising an organosiloxane material having a (weight average)
molecular weight of from 500 to 100,000 g/mol.
11. The thin film according to any of the preceding claims,
comprsing an organosiloxane material, which has a repeating
-M-O-M-O- backbone having a first organic substituent bound to the
backbone, the material having a molecular weight of from 500 to
100,000 g/mol, where M is silicon and O is oxygen, and the film
exhibiting one or several of the following properties: a k value of
2.9 or less or even more preferably 2.5 or less, a CTE 30 ppm or
less, and Young's modulus 4 GPa or more.
12. An object comprising a low k dielectric film, the film
comprising a material according to any of claims 1 to 10.
13. A method of forming a thin film having a dielectric constant of
2.9 or less, comprising polymerizing a monomer having the formula
I: ##STR18## wherein R.sub.1, R.sub.2 and R.sub.3 have the same
meaning as above, to form a siloxane material; depositing the
siloxane material in the form of a thin layer; and curing the thin
layer to form a film.
14. The method according to claim 13, comprising homopolymerizing a
monomer having the formula I or copolymerizing isomers thereof in a
liquid medium formed by a first solvent to form a hydrolyzed
product comprising a siloxane material; depositing the hydrolyzed
product on the substrate as a thin layer; and curing the thin layer
to form a thin film having a thickness of 0.01 to 10 um.
15. The method according to claim 13 or 14, comprising
homopolymerizing a monomer having the formula I or copolymerizing
isomers thereof in a liquid medium formed by a first solvent to
form a hydrolyzed product comprising a siloxane material;
recovering the hydrolyzed product; mixing the hydrolyzed product
with a second solvent to form a solution; applying the solution on
a substrate; removing the second solvent to deposit the hydrolyzed
product on the substrate as a thin layer; and curing the thin layer
to form a thin film having a thickness of 0.01 to 10 um.
16. The method according to claim 14 or 15, comprising carrying out
the step of homopolymerising to form a polymerized product and the
step of curing the hydrolyzed product at a temperature of 50 to
425.degree. C.
17. The method according to any of claims 13 to 16, comprising
depositing the siloxane material on a substrate of a semiconductor
device; and patterning the siloxane material to form a dielectric
in a semiconductor device.
18. The method according to claim 17, comprising patterning the
siloxane material by removing siloxane material in selected areas
and depositing an electrically conductive material in the selected
areas.
19. The method according to claim 18, wherein a barrier layer is
deposited in the selected areas prior to depositing the
electrically conductive material.
20. The method according to claim 18, wherein the electrically
conductive material is deposited in the selected areas without a
barrier layer, and wherein the electrically conductive material
comprises aluminum or copper.
21. The method according to claim 13, comprising carrying our
polymerization at conditions conducive to cross-linking between the
monomer units so as to form a siloxane material; depositing the
siloxane material on a substrate; heating the siloxane material to
cause further cross-linking; patterning the siloxane material to
remove siloxane material in selected areas; adding an electrically
conductive material in the selected areas; and performing chemical
mechanical polishing on the electrically conductive material down
to the siloxane material.
22. The method according to claim 21, wherein the siloxane material
is patterned by selectively exposing the siloxane material to
electromagnetic energy and removing non-exposed areas of siloxane
material with a developer.
23. The method according to claim 22, wherein the siloxane material
is patterned by RIE.
24. The method according to any of claims 21 to 23, wherein the
patterning is performed without a capping layer.
25. The method according to any of claims 13 to 24, wherein the
siloxane material is deposited on a substrate of a semiconductor
device, and the siloxane material is heated to cause further
cross-linking, whereby a film is obtained, having a shrinkage after
heating of less than 10%, preferably less than 5%, in particular
less than 2%, and a thermal stability of more 425.degree. C.
26. The method according to any of claims 13 to 25, wherein the
compound of formula I is obtained from a compound of formula I
wherein R.sub.2 stands for hydrogen and R.sub.1 and R.sub.3 have
the same meanings as above.
27. The method according to claim 26, wherein the compound of
formula I, wherein R.sub.2 stands for hydrogen, is selectively
produced by hydrosilylation of halosubstituted silanes in the
presence of a cobalt octoate catalyst.
28. The method according to any of claims 13 to 27, wherein the
film is baked after spin coating at a temperature below about
200.degree. C. and then cured by exposure to UV radiation
simultaneously with a thermal treatment at a temperature below
450.degree. C. for 0.1 to 20 minutes.
29. The method according to claim 28, wherein the curing is carried
out for a sufficient period of time for reacting the organic
substitutent at position R.sub.2 of the unit derived from a monomer
having the formula I above.
30. A method of producing silane-based materials by
hydrosilylation, wherein the reaction is carried out in the
presence of cobalt octacarbonyl as a catalyst.
31. The method according to claim 30, wherein a trihalosilane is
reacted with a dihalosilane in the presence of cobalt
octacarbonyl.
32. The method according to claim 30 or 31, wherein a trihalosilane
is used having a reactive organic group comprising an unsaturated
bond.
33. The method according to claim 31 or 32, wherein
vinyltrichlorosilane is reacted with dichlorosilane to form
1,1,1,4,4-pentachloro-1,4-disilabutane.
Description
[0001] This application claims priority of U.S. Provisional
Application for Patent Ser. No. 60/689,541 filed Jun. 13, 2005,
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method making novel
organo functionalized silane precursors and polymers of the same
that are applicable for thin films used for example as dielectrics
in integrated circuits, optoelectronic applications and for other
similar applications. In particular, the invention concerns first
making an intermediate monomer and then converting the monomer to
an organo functionalized silane monomer and finaly forming a
polymer or polymer compositions of the functionalized monomers. The
invention also concerns a method for producing such films by
preparing siloxane compositions by polymerization of the organo
functionalized monomers, by applying the polymerized compositions
on a substrate in the form of a layer and by curing the layer to
form a film. Further, the invention concerns integrated circuit and
optoelectronic devices and methods of manufacturing them.
[0004] 2. Description of Related Art
[0005] Built on semiconductor substrates, integrated circuits
comprise millions of transistors and other devices, which
communicate electrically with one another and with outside
packaging materials through multiple levels of vertical and
horizontal wiring embedded in a dielectric material. Within the
metallization structure, "vias" make up the vertical wiring,
whereas "interconnects" form the horizontal wiring. Fabricating the
metallization can involve the successive depositing and patterning
of multiple layers of dielectric and metal to achieve electrical
connection among transistors and to outside packaging material. The
patterning for a given layer is often performed by a multi-step
process comprising layer deposition, photoresist spin, photoresist
exposure, photoresist develop, layer etch, and photoresist removal
on a substrate. Alternatively, the metal may sometimes be patterned
by first etching patterns into a layer of a dielectric material,
filling the pattern with metal, then subsequently
chemically/mechanically polishing the metal so that the metal
remains embedded only in the openings of the dielectric. As an
interconnect material, aluminum has been utilized for many years
due to its high conductivity, good adhesion to SiO.sub.2, known
processing methods (sputtering and etching) and low cost. Aluminum
alloys have also been developed over the years to improve the
melting point, diffusion, electromigration and other qualities as
compared to pure aluminum. Spanning successive layers of aluminum,
tungsten has traditionally served as the conductive via plug
material.
[0006] In IC's, silicon dioxide, having a dielectric constant of
around 4.0, has been the dielectric of choice, used in conjunction
with aluminum-based and tungsten-based interconnects and via for
many years.
[0007] The drive to faster microprocessors and more powerful
electronic devices in recent years has resulted in very high
circuit densities and faster operating speeds which--in turn--have
required that higher conductivity metals and significantly lower-k
dielectrics compared to silicon dioxide (preferably below 3.0) be
used. In the past few years, VLSI (and ULSI) processes have been
moving to copper damascene processes, where copper (or a copper
alloy) is used for the higher conductance in the conductor lines
and a spin-on or CVD process is used for producing low-k
dielectrics which can be employed for the insulating material
surrounding the conductor lines. To circumvent problems with
etching, copper along with a barrier metal is blanket deposited
over recessed dielectric structures consisting of interconnect and
via openings and subsequently polished in a processing method known
as the "dual damascene." The bottom of the via opening is usually
the top of an interconnect from the previous metal layer or, in
some instances, the contacting layer to the substrate.
[0008] Summarizing: aside from possessing a low dielectric
constant, the ideal dielectric should have the following
properties:
[0009] 1. High modulus and hardness in order to bind the maze of
metal interconnects and vias together in particular in the final
chip packaging step as well as abet chemical mechanical polishing
processing steps.
[0010] 2. Low thermal expansion, typically less than or equal to
that of metal interconnects.
[0011] 3. Excellent thermal stability, generally in excess of
350.degree. C., but more often even better than 500.degree. C.
after final curing.
[0012] 4. No cracking even as thick films structures, excellent
fill and planarization properties.
[0013] 5. Excellent adhesion to dielectric, semiconductor,
diffusion barrier and metal materials.
[0014] 6. Sufficient thermal conductivity to dissipate joule
heating from interconnects and vias.
[0015] 7. Material density that precludes absorption of solvents,
moisture, or reactive gasses.
[0016] 8. Allows desired etch profiles at very small
dimensions.
[0017] 9. Low current leakage, high breakdown voltages, and low
loss-tangents.
[0018] 10. Stable interfaces between the dielectric and contacting
materials.
[0019] By necessity, low-k materials are usually engineered on the
basis of compromises.
[0020] Organic polymers can be divided into two different groups
with respect to the behavior of their dielectric constant.
Non-polar polymers contain molecules with almost purely covalent
bonds. Since they mainly consist of non-polar C--C bonds, the
dielectric constant can be estimated using only density and
chemical composition. Polar polymers do not have low loss, but
rather contain atoms of different electronegativity, which give
rise to an asymmetric charge distribution. Thus polar polymers have
higher dielectric loss and a dielectric constant, which depends on
the frequency and temperature at which they are evaluated. Several
organic polymers have been developed for dielectric purposes.
However, applicability of these films is limited because of their
low thermal stability, softness, and incompatibility with
traditional technological processes developed for SiO.sub.2 based
dielectrics.
[0021] Therefore most of the current developments are focusing on
SSQ (silsesquioxane or siloxane) or silica based dielectric
materials. For SSQ based materials, silsesquioxane (siloxane) is
the elementary unit. Silsesquioxanes, or T-resins, are
organic-inorganic hybrid polymers with the empirical formula
(R--SiO.sub.3/2).sub.n. The most common representative of these
materials comprise a ladder-type structure, and a cage structure
containing eight silicon atoms placed at the vertices of a cube
(T.sub.8 cube) on silicon can include hydrogen, alkyl, alkenyl,
alkoxy, and aryl. Many silsesquioxanes have reasonably good
solubility in common organic solvents due to their organic
substitution on Si. The organic substitutes provide low density and
low dielectric constant matrix material. The lower dielectric
constant of the matrix material is also attributed to a low
polarizability of the Si--R bond in comparison with the Si--O bond
in SiO.sub.2. The silsesquioxane based materials for
microelectronic application are mainly hydrogen-silsesquioxane,
HSQ, and methyl-silsesquioxane, (CH.sub.3--SiO.sub.3/2).sub.n(MSQ).
MSQ materials have a lower dielectric constant as compared to HSQ
because of the larger size of the CH.sub.3 group .about.2.8 and
3.0-3.2, respectively and lower polarizability of the Si--CH.sub.3
bond as compared to Si--H.
[0022] The silica-based materials have the tetrahedral basic
structure of SiO.sub.2. Silica has a molecular structure in which
each Si atom is bonded to four oxygen atoms. Each silicon atom is
at the center of a regular tetrahedron of oxygen atoms, i.e., it
forms bridging crosslinks. All pure of silica have dense structures
and high chemical and excellent thermal stability. For example,
amorphous silica films, used in microelectronics, have a density of
2.1 to 2.2 g/cm.sup.3. However, their dielectric constant is also
high ranging from 4.0 to 4.2 due to high frequency dispersion of
the dielectric constant which is related to the high polarizability
of the Si--O bonds. Therefore, it is necessary to replace one or
more Si--O--Si bridging groups with C-containing organic groups,
such as CH.sub.3 groups, which lowers the k-value. However, these
organic units reduce the degrees of bridging crosslinks as well
increases the free volume between the molecules due to steric
hindrance. Therefore, their mechanic strength (Young's modulus<6
GPa) and chemical resistance is reduced compared to tetrahedral
silicon dioxide. Also, these methyl-based silicate and SSQ (i.e.,
MSQ) polymers have relatively low cracking threshold, typically on
the order of 1 um or less.
[0023] Quite recently there have been some efforts to develop
enhanced MSQ polymers by co-polymerizing them with disilanes, i.e.,
bistrimethoxysilane, that contain bridging alkyl groups between
silanes and thus crosslinking density has been increased. However,
these materials still contain significant amount of methyl-based
silanes, i.e. methyl-trimethoxysilane, as comonomers and due to
methyl co-polymer nature only moderate Young's modulus and hardness
properties has been obtained, with dielectric constant of around
2.93.
SUMMARY OF THE INVENTION
[0024] It is an object of the present invention to provide a silane
intermediate monomer.
[0025] It is another object to provide a method of modifying the
monomer so as to form a novel organo-functionalized molecule.
[0026] It is a third object of the invention to provide methods of
producing poly(organo siloxane) compositions, which are suitable
for the preparation of thin films having excellent dielectric
properties.
[0027] It is a fourth object of the invention, to provide novel
thin films, having low dielectric constant, excellent mechanical
and thermal properties, said films being formed by the
above-mentioned polymer.
[0028] It is a fifth object of the invention to provide dielectric
layers on silicon wafers.
[0029] It is a still a sixth object of the invention is to provide
light (preferably UV wavelength) enhanced curing for the
poly(organo siloxane) film containing novel organic moieties.
[0030] These and other objects, together with the advantages
thereof over the known dielectric thin films and methods for the
preparation thereof, which shall become apparent from specification
which follows, are accomplished by the invention as hereinafter
described and claimed.
[0031] In order to achieve these objectives in the present
invention, novel polyorgano silsesquioxane materials, which are
based on multisilane molecules, and useful as interlayer insulating
films for semiconductor or optoelectronic devices, are
introduced.
[0032] Generally, the monomer of the novel materials comprises at
least two metal atoms, which are interconnected by a bridging
hydrocarbyl radical and which exhibit hydrolysable substitutents on
both of the metal atoms along with at least one organic group which
is capable of reducing the polarizability of the polymer, further
cross-linking the polymer, forming nanometer size porosity to the
polymer or combination of all previous properties formed from the
monomer.
[0033] In particular, the metal atoms are silicon atoms, and the
bridging radical is a linear or branched (bivalent) hydrocarbyl
group which links the two silicon atoms together. Furthermore,
typically one of the silicon atoms contains three hydrolysable
groups and the other silicon atom contains two hydrolysable groups
and an organic cross-linking group, reactive cleaving group or
polarizability reducing organic group, such as an alkyl, alkenyl,
alkynyl, aryl, polycyclic group or organic containing silicon
group. The latter group may also be fully or partially
fluorinated.
[0034] The general formula I of the precursor used in the present
invention is the following: ##STR2## wherein: [0035] R.sub.1 is a
hydrolysable group, such as hydrogen, a halide, an alkoxy or an
acyloxy group, [0036] R.sub.2 is hydrogen, an organic crosslinking
group, a reactive cleaving group or a polarizability reducing
organic group, and [0037] R.sub.3 is a bridging linear or branched
bivalent hydrocarbyl group.
[0038] In the method of the invention, formula I covers two
slightly different kinds of precursors, viz. a first initial
precursor corresponds to formula I wherein R.sub.2 stand for
hydrogen. The second kind of precursor have formula I wherein
R.sub.2 stands for an organic cross-linking group, a reactive
cleaving group or a polarizability reducing organic group, or
combinations thereof. These groups are represented by alkyl,
alkenyl, alkynyl, aryl, polycyclic groups and organic-containing
silicon groups.
[0039] Compounds according to the formula wherein R.sub.2 group is
hydrogen can be formed by a hydrosilylation reaction wherein a
trihalosilane and a dihalosilane are reacted in the presence of
cobalt octacarbonyl so as to form a
1,1,1,4,4-pentahalo-1,4-disilabutane intermediate at good yield.
This intermediate can be converted by, e.g. hydrosilylation, to
replace hydrogen at position R.sub.2 so as to form an
organo-functionalized silane. If R.sub.2 group is a reactive group,
the group may decompose during the film curing procedure and leave
behind a cross-linking group or polarizability reducing group or a
combination thereof.
[0040] The polymer of the present invention is produced by
hydrolysing the hydrolysable groups of the multisilane monomer or a
combination of the polymer described in the invention or a
combination of molecules of the invention and molecules known in
the art and then further polymerising it by a condensation
polymerisation process.
[0041] The new material can be used as a low k dielectric film in
an object comprising e.g. a (silicon) wafer.
[0042] The present invention also provides a method of forming a
thin film having a dielectric constant of 2.9 or less or more
preferably 2.5 or less, comprising a monomer having the formula I,
to form a siloxane material, depositing the siloxane material in
the form of a thin layer; and curing the thin layer to form a
film.
[0043] Considerable advantages are obtained by the present novel
materials and by the methods of manufacturing them. Thus, the
present invention presents a solution for existing problems related
to low-k dielectric polymers, more specifically mechanical
properties (modulus and hardness), cracking threshold and thermal
properties, also applicable to aluminum reflow processing
temperatures. The film is also particularly applicable to light or
radiation (preferably UV wavelength or e-beam) enhanced curing,
optionally carried out simultaneously with the thermal curing
process.
[0044] The novel organo-functionalized molecule can be built into
such a form that it is capable of further reacting in the matrix.
This means, for example, that the organic function of the molecule
can undergo cross-linking, cleaving or combination of both, i.e.,
subsequent cleaving and cross-linking reactions.
[0045] The present invention provides excellent chemical resistance
and very low chemical adsorption behavior due to high cross-linking
bridging group density.
[0046] If R.sub.2 group is a cleaving group still very small pore
size is resulted in, i.e., typically 1.5 nm or less. However, the
polymer formed according to innovation is also compatible with
traditional type porogens such as cyclodextrin, which can be used
to form micro-porosity into the polymer and thus reduce the
dielectric constant of the polymer.
[0047] Another important advantages is that the novel low-k
dielectric materials have excellent properties of planarization
resulting in excellent local and global planarity on top a
semiconductor substrate topography, which reduces or even fully
eliminates the need for chemical mechanical planarization after
dielectric and oxide liner deposition.
[0048] Furthermore, the novel materials have excellent gap fill
properties.
[0049] In summary, the present invention provides a low dielectric
constant siloxane polymer applicable to forming thermally and
mechanically stable, dense dielectric films exhibiting
high-cracking threshold, low pore volume and pore size. The polymer
will give a non-aqueous and silanol free film with excellent local
and global planarization as well as gap fill after subjected to
thermal treatment with having excellent electrical properties. A
film made out of the novel polymer remains structurally,
mechanically and electrically unchanged after final cure even if
subjected to temperatures higher than the final cure temperature.
All these properties, as they are superior over conventional low
dielectric constant polymers, are crucial to overcome existing
problems in low dielectric constant film integration to a
semiconductor device.
[0050] Next, the invention will be examined more closely by means
of the following detailed description and with reference to a
number of working examples.
DETAILED DESCRIPTION OF THE INVENTION
[0051] The present invention provides a low dielectric constant
polymer comprising at least one multisilane mononer unit with at
least one organic bridging group between silicon atoms. In
addition, one of the silicon atoms also contains one organic
cross-linking group, reactive cleaving group, polarizability
reducing organic group or a combination of all previous such as an
alkyl, alkenyl, alkynyl, aryl, polycyclic group or organic
containing silicon group.
[0052] One of the silicon atoms comprises two hydrolysable groups
and the other three hydrolysable groups capable of forming a
continuous siloxane backbone matrix once hydrolyzed and
polymerized, such as hydrogen, halide, alkoxy or acyloxy groups,
but most preferably chlorine or ethoxide groups.
[0053] The general formula I of the precursor used for
polymerization in the present invention is the following: ##STR3##
wherein: [0054] R.sub.1 is a hydrolysable group [0055] R.sub.2 is
an organic crosslinking group, reactive cleaving group,
polarizability reducing organic group or combination of all
previous, such as an alkyl, alkenyl, alkynyl, aryl, polycyclic
group or organic containing silicon group, and [0056] R.sub.3 is a
bridging linear or branched bivalent hydrocarbyl group.
[0057] R.sub.1 is preferably selected from the group of halides,
alkoxy groups, acyloxy groups and hydrogen, R.sub.2 is preferably
selected from alkyl groups, alkenyl groups, alkynyl and aryl
groups, polycyclic group or organic containing silicon group, and
R.sub.3 is preferably selected from linear and branched alkylene
groups, alkenylene groups and alkynylene groups, bivalent alicyclic
groups (polycyclic groups) and bivalent aromatic groups which all
are included in the definition of a bivalent hydrocarbyl group.
[0058] The cured composition obtained by essentially
homopolymerizing monomers of the above formula, with subsequent
curing to achieve cross-linking, comprises a cross-linked
organosiloxane polymer, i.e. poly(organosiloxane). It can be formed
into a thin film.
[0059] `Alkenyl` as used herein includes straight-chained and
branched alkenyl groups, such as vinyl and allyl groups. The term
`alkynyl` as used herein includes straight-chained and branched
alkynyl groups, suitably acetylene. `Aryl` means a mono-, bi-, or
more cyclic aromatic carbocyclic group, substituted or
non-substituted; examples of aryl are phenyl, naphthyl, or
pentafluorophenyl propyl. `polycyclic` group used herein includes
for example adamantyl, dimethyl adamantyl propyl, norbornyl or
norbornene. More specifically, the alkyl, alkenyl or alkynyl may be
linear or branched.
[0060] The bivalent alicyclic groups may be polycyclic aliphatic
groups including residues derived from ring structures having 5 to
20 carbon atoms, such as norbornene (norbornenyl) and adamantyl
(adamantylene). "Arylene" stands for bivalent aryls comprising 1 to
6 rings, preferably 1 to 6, and in particular 1 to 5, fused rings,
such as phenylene, naphthylene and anthracenyl.
[0061] Alkyl contains preferably 1 to 18, more preferably 1 to 14
and particularly preferred 1 to 12 carbon atoms. The alkyl is
preferably branched at the alpha or beta position with one and
more, preferably two, C.sub.1 to C.sub.6 alkyl groups, especially
preferred halogenated, in particular partially or fully fluorinated
or per-fluorinated alkyl, alkenyl or alkynyl groups. Some examples
are non-fluorinated, partially fluorinated and per-fluorinated
i-propyl, t-butyl, but-2-yl, 2-methylbut-2-yl, and
1,2-dimethylbut-2-yl. In particular, the alkyl group is a lower
alkyl containing 1 to 6 carbon atoms, which optionally bears 1 to 3
substituents selected from methyl and halogen. Methyl, ethyl,
n-propyl, i-propyl, n-butyl, i-butyl and t-butyl are particularly
preferred.
[0062] Alkenyl contains preferably 2 to 18, more preferably 2 to 14
and particularly preferred 2 to 12 carbon atoms. The ethylenic,
i.e. two carbon atoms bonded with double bond, group is preferably
located at the position 2 or higher, related to the Si or M atom in
the molecule. Branched alkenyl is preferably branched at the alpha
or beta position with one and more, preferably two, C.sub.1 to
C.sub.6 alkyl, alkenyl or alkynyl groups, particularly preferred
fluorinated or per-fluorinated alkyl, alkenyl or alkynyl
groups.
[0063] Alkynyl contains preferably 3 to 18, more preferably 3 to 14
and particularly preferred 3 to 12 carbon atoms. The ethylinic
group, i.e. two carbon atoms bonded with triple bond, group is
preferably located at the position 2 or higher, related to the Si
or M atom in the molecule. Branched alkynyl is preferably branched
at the alpha or beta position with one and more, preferably two,
C.sub.1 to C.sub.6 alkyl, alkenyl or alkynyl groups, particularly
preferred per-fluorinated alkyl, alkenyl or alkynyl groups.
[0064] The aryl group is preferably phenyl, which optionally bears
1 to 5 substituents selected from halogen, alkyl or alkenyl on the
ring, or naphthyl, which optionally bear 1 to 11 substituents
selected from halogen alkyl or alkenyl on the ring structure, the
substituents being optionally fluorinated (including
per-fluorinated or partially fluorinated)
[0065] The polycyclic group is for example adamantyl, dimethyl
adamantyl propyl, norbornyl or norbornene, which optionally bear
1-8 substituents or can be also optionally `spaced` from the
silicon atom by alkyl, alkenyl, alkynyl or aryl groups containing
1-12 carbons.
[0066] "Hydrolysable group" stands for halogen (chlorine, fluorine,
bromine), alkoxy (in particular C.sub.1-10 alkoxy, such as methoxy,
ethoxy, propoxy, or butoxy), acyloxy, hydrogen or any other group
that can easily be cleaved off the monomer during polymerization,
e.g. condensation polymerization.
[0067] The alkoxy groups stand generally for a group having the
formula R.sub.4O--, wherein R.sub.4 stands for an alkyl as defined
above. The alkyl residue of the alkoxy groups can be linear or
branched. Typically, the alkoxy groups are comprised of lower
alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy
and t-butoxy groups.
[0068] The acyloxy groups have the general formula
R.sub.5O.sub.2--, wherein R.sub.5 stands for an alkyl as defined
above. In particular, the alkyl residue of the acyloxy group can
have the same meanings as the corresponding residue in the alkoxy
group.
[0069] In the context of the disclosure the organic group
substituent halogen may be a F, Cl, Br or I atom and is preferably
F or Cl. Generally, term `halogen` herein means a fluorine,
chlorine, bromine or iodine atom.
[0070] In the monomer of formula I, the silicon atoms are linked to
each other via a linker group. Typically, the linker comprises 1 to
20, preferably about 1 to 10, carbon atoms. Examples of suitable
linker groups R.sub.3 include alkylene, alkenylene and alkynylene
groups. "Alkylene" groups generally have the formula
--(CH.sub.2).sub.r-- in which r is an integer 1 to 10. One or both
of the hydrogens of at least one unit --CH.sub.2-- can be
substituted by any of the substituents mentioned below. The
"alkenylene" groups correspond to alkylene residues, which contain
at least one double bond in the hydrocarbon backbone. If there are
several double bonds, they are preferably conjugated. "Alkynylene"
groups, by contrast, contain at least one triple bond in the
hydrocarbon backbone corresponding to the alkylene residues.
[0071] The bivalent linker residue can be unsubstituted or
substituted. The substitutents are preferably selected from the
group of fluoro, bromo, C.sub.1-10-alkyl, C.sub.1-10-alkenyl,
C.sub.6-18-aryl, acryl, epoxy, carboxyl and carbonyl groups. A
particularly interesting alternative is comprised of methylene
groups substituted with at least one alkyl group, preferably a
lower alkyl group or 1 to 4 carbon atoms. As a result of the
substitution, a branched linker chain is obtained. The branched
linker chain, e.g. --CH(CH.sub.3)-- can contain in total as many
carbon atoms as the corresponding linear, e.g.
--CH.sub.2CH.sub.2--, even if some of the carbon atoms are located
in the side chain, as shown below in connection with the working
examples. Such molecules can be considered "isomeric", for the
purpose of the present invention.
[0072] As examples of a particularly preferred compounds according
to formula I, 1-(trichlorosilyl)-2-(methyldichlorosilyl) ethane and
1-(methyldichlorosilyl)-1-(trichlorosilyl) ethane can be
mentioned.
[0073] As mentioned above, in a first step of the method according
to the present invention, a monomer is produced having the formula:
##STR4## wherein: [0074] R.sub.1 is a hydrolysable group [0075]
R.sub.2 is hydrogen, and [0076] R.sub.3 is a bridging linear or
branched bivalent hydrocarbyl group.
[0077] This monomer and similar silane-based materials can be
produced by hydrosilylation, which is carried out in the presence
of cobalt octacarbonyl as a catalyst.
[0078] In particular, the novel hydrosilylation reaction catalyzed
in the presence of cobalt octacarbonyl or, generally, any similar
transition metal octate catalyst, is using halosilanes as
reactants. Thus, in order to produce, at high yield, a compound of
the formula above, in which R.sub.2 stands for hydrogen, a first
trihalogenated silane compound can be reacted with a second
dihalogenated silane compound in the present of cobalt
octacarbonyl. The trihalosilane used typically has a reactive
organic group comprising an unsaturated bond for facilitating the
hydrosilylation reaction.
[0079] This reaction is illustrated below in Example 1, wherein
vinyltrichlorosilane is reacted with dichlorosilane to form
1,1,1,4,4-pentachloro-1,4-disilabutane.
[0080] Surprisingly, by the method disclosed, the desired compound
is obtained with high purity, which allows for the use of the
monomer as a precursor for the following steps of the preparation
of siloxane materials by incorporation of desired substitutents at
the R.sub.2 position.
[0081] The present invention provides a low dielectric constant
siloxane polymer applicable for forming thermally and mechanically
stable, high cracking threshold, dense and low pore volume and pore
size dielectric film. The polymer results in water and silanol free
film with excellent local and global planarization as well as gap
fill after subjected to thermal treatment with having excellent
electrical properties. A film made out of the invented polymer
remains structurally, mechanically and electrically unchanged after
final cure even if subjected to temperatures higher than the final
cure temperature. All these properties, as they are superior over
conventional low dielectric constant polymers, are crucial to
overcome existing problems in low dielectric constant film
integration to a semiconductor device.
[0082] The polymerization synthesis is based on hydrolysis and
condensation chemistry synthesis technique. Polymerization can be
carried out in melt phase or in liquid medium. The temperature is
in the range of about 20 to 200.degree. C., typically about 25 to
160.degree. C., in particular about 80 to 150.degree. C. Generally
polymerization is carried out at ambient pressure and the maximum
temperature is set by the boiling point of any solvent used.
Polymerization can be carried out at refluxing conditions. It is
possible to polymerize the instant monomers without catalysts or by
using alkaline or, in particular, acidic catalysts.
[0083] The present organosiloxane materials have a (weight average)
molecular weight of from 500 to 100,000 g/mol. The molecular weight
can be in the lower end of this range (e.g., from 500 to 10,000
g/mol, or more preferably 500 to 8,000 g/mol) or the organosiloxane
material can have a molecular weight in the upper end of this range
(such as from 10,000 to 100,000 g/mol or more preferably from
15,000 to 50,000 g/mol). It may be desirable to mix a polymer
organosiloxane material having a lower molecular weight with a
organosiloxane material having a higher molecular weight.
[0084] We have found that a suitable polymer composition can be
obtained by homopolymerizing a monomer of formula I comprising
either a linear or a branched linker group. However, it is also
possible to provide a composition that is obtained by
copolymerizing first monomers having formula I, wherein R.sub.3
stands for a linear bivalent hydrocarbyl residue, with second
monomers having formula I, wherein R.sub.3 stands for a branched
bivalent hydrocarbyl residue, the molar ratio of the first monomers
to the second monomers is 95:5 to 5:95, in particular 90:10 to
10:90, preferably 80:20 to 20:80.
[0085] According to one preferred embodiment, in order to modify
the properties, the siloxane material deposited on a substrate of a
semiconductor device is heated to cause further cross-linking,
whereby a film is obtained, having a shrinkage after heating of
less than 10%, preferably less than 5%, in particular less than 2%,
and a thermal stability of more 425.degree. C.
[0086] According to a particular embodiment, the film is baked
after spin coating at a temperature below about 200.degree. C. and
then cured by exposure to UV radiation simultaneously with a
thermal treatment at a temperature below 450.degree. C. for 0.1 to
20 minutes. The curing is carried out for a sufficient period of
time for reacting the organic substituent at position R.sub.2 of
the unit derived from a monomer having the formula I above.
[0087] The polymer of the present invention is capable of forming
low dielectric films having a dielectric constant of 3.0 or less,
in particular 2.9 or less, preferably about 2.5 to 1.9, a Young's
modulus of 10.0 GPa or more, a porosity of 5% or less and cracking
threshold of 2 urn or more after subjected to thermal treatment.
Also the film formed from the polymer using a multisilane component
remains stable on a semiconductor structure at temperatures up to
500.degree. C. or more after subjecting the film for thermal
treatment at 450.degree. C. or less for 1 hour or less.
[0088] As mentioned above, the present invention also provides
methods of producing integrated circuit devices. Such methods
typically comprise the steps of:
[0089] forming a plurality of transistors on a semiconductor
substrate;
[0090] forming multilayer interconnects by: [0091] depositing a
layer of metal; [0092] patterning the metal layer; [0093]
depositing a first dielectric material having a first modulus and a
first k value; [0094] depositing a second dielectric material
having a second modulus higher than the first modulus of the first
material and with a k value lower than the first k value of the
first material; and [0095] patterning the first and second
dielectric materials and depositing a via filling metal material
into the patterned areas.
[0096] The material according to the invention used for the first
dielectric layer is preferably an organosiloxane material, which
has a repeating -M-O-M-O- backbone having a first organic
substituent bound to the backbone, the material having a molecular
weight of from 500 to 100,000 g/mol, where M is silicon and O is
oxygen. The molecular weight is from 1500 to 30,000 g/mol, and it
preferably exhibits one or several of the following properties:
[0097] a k value of 2.9 or less or even more preferably 2.5 or
less, [0098] a CTE 30 ppm or less, and [0099] Young's modulus 4 GPa
or more.
[0100] Due to the excellent properties of planarization, the
patterning step can be carried out without a preceding step of
chemical mechanical planarization. Alternatively, 45% or less of
the total thickness of the second dielectric material is removed by
performing chemical mechanical planarization on the second
dielectric material.
[0101] The organosiloxane material can be deposited by polymerizing
a monomer of formula I in a liquid medium formed by a first solvent
to form a hydrolyzed product comprising a siloxane material;
depositing the hydrolyzed product on the substrate as a thin layer;
and curing the thin layer to form a thin film having a thickness of
0.01 to 10 um.
[0102] Whereas one of the dielectric materials comprises a material
in accordance with the present invention, the other material can be
a known, organic, inorganic, or organic/inorganic material, e.g. of
the kind discussed above in the introductory portion of the
description.
[0103] Generally, the organosiloxane material is a spin coated
material.
[0104] The organosiloxane material is an organic-inorganic and has
a coefficient of thermal expansion of 12 to 20 ppm. It can have a
dielectric constant of 2.7 or less.
[0105] Further details of the invention will be discussed in
connection with the following working examples:
EXAMPLES
Example 1
1,1,1,4,4-Pentachloro-1,4-disilabutane (The Intermediate)
[0106] ##STR5##
[0107] Vinyltrichlorosilane (68.8 g, 426 mmol) and cobalt
octacarbonyl (700 mg) were placed in a 100 mL rb flask and cooled
in an ice bath to 0.degree. C. Dichlorosilane (bp. 8.degree. C.,
44.3 g, 439 mmol) was then condensed into the flask, The system was
allowed to warm up to room temperature during night. Distillation
at 60 . . . 62.degree. C./8 mbar gave
1,1,1,4,4-Pentachloro-1,4-disilabutane (120.8 g, 460 mmol) in 93%
yield.
Example 2
Tris(3,3,6,6,6-pentachloro-3,6-disilahexyl)chlorosilane
[0108] ##STR6##
[0109] 11.00 g (0.076 mol) trivinylchlorosilane was added to a 100
ml vessel followed by 2 ml 1,1,1,4,4-pentachloro-1,4-disilabutane.
The solution was heated to 80.degree. C. and 15 .mu.L of a 10%
H.sub.2PtCl.sub.6/IPA-solution was added. Strong exothermic
reaction was observed and heat was switched off. Rest of
1,1,1,4,4-pentachloro-1,4-disilabutane was added slowly during 30
min keeping the temperature of the solution below 130.degree. C.
The total amount of 1,1,1,4,4-pentachloro-1,4-disilabutane was
61.50 g (0.234 mol, 2.6% excess). After addition heat was again
switched on and solution was stirred for an hour at 110.degree. C.
After that solution was distilled yielding 47.08 g (66%)
tris(3,3,6,6,6-pentachloro-3,6-disilahexyl)chlorosilane. B.p.
264.degree. C./<0.5 mbar.
Example 3
1,1,1,4,4,7,7,7-Octachloro-1,4,7-trisilaheptane
[0110] ##STR7##
[0111] Vinyltrichlorosilane (16.8 g, 104 mmol) was heated to
60.degree. C. and 100 .mu.L 10% H.sub.2PtCl.sub.6/IPA-solution was
added. 1,1,1,4,4-pentachloro-1,4-disilabutane (20.4 g, 77.7 mmol)
was added slowly during 20 min so that the temperature did not
exceed 100.degree. C. The reaction was allowed to proceed for 12
hours at 100.degree. C., after which it was distilled under vacuum
at 115-130.degree. C./<1 mbar. The yield was 31.5 g (74.3 mmol,
96%).
Example 4
1,1,1,4,4,7,7,7-Octachloro-1,4,7-trisilaoctane
[0112] ##STR8##
[0113] 1,1,1,4,4-Pentachloro-1,4-disilabutane (51.6 g, 196 mmol)
was heated to 80.degree. C. and 20 .mu.L 10%
H.sub.2PtCl.sub.6/IPA-solution was added. Vinylmethyldichlorosilane
(29.7 g, 210 mmol) was added slowly during 20 min so that the
temperature did not exceed 130.degree. C. The reaction was allowed
to proceed for 11/2 hours, after which it was distilled under
vacuum at 90-102.degree. C./<1 mbar. The yield was 70.2 g (174
mmol, 89%).
Examples 5 to 7
1,1,1,4,4-Pentachloro-1,4-disiladecane
1,1,1,4,4-Pentachloro-1,4-disiladodecane
1,1,1,4,4-Pentachloro-1,4-disilatetrakaidecane
[0114] ##STR9##
[0115] 32 ml (21.53 g, 0.256 mol) 1-hexene and 20 .mu.l
H.sub.2PtCl.sub.6/IPA solution were added to a 100 ml vessel.
Solution was heated up to 80.degree. C. and 46.90 g (0.179 mol)
1,1,1,4,4-pentachloro-1,4-disilabutane was added slowly during 30
min. Heat was switched off when exothermic reaction was observed.
Temperature during the addition was kept below 130.degree. C. After
addition heat was again switched on and solution was stirred for an
hour at 110.degree. C. After that product was purified by
distillation. B.p. 100.degree. C./0.8 mbar. Yield 50.40 g (81.4%).
1-hexene can be replaced by 1-octene or 1-decene to produce
1,1,1,4,4-pentachloro-1,4-disiladodecane (b.p. 131.degree. C./0.7
mbar, 88% yield) and 1,1,1,4,4-pentachloro-1,4disilatetrakaidecane
(b.p.138.degree. C./0.8 mbar, 82% yield), respectively.
Example 8
1,1,1,4,4-Pentachloro-7-phenyl-1,4-disilaheptane
[0116] ##STR10##
[0117] 18.77 g (0.159 mol) allylbenzene and 50 .mu.l
H.sub.2PtCl.sub.6/IPA solution were added to a 100 ml vessel.
Solution was heated up to 80.degree. C. and 41.85 g (0.159 mol)
1,1,1,4,4-pentachloro-1,4-disilabutane was added slowly during 30
min. Heat was switched off when exothermic reaction was observed.
Temperature during the addition was kept below 130.degree. C. After
addition heat was again switched on and solution was stirred for an
hour at 110.degree. C. After that product was purified by
distillation. B.p. 137.degree. C./0.8 mbar. Yield 35.10 g
(58%).
Example 9
1,1,1,4,4-Pentachloro-6-pentafluorophenyl-1,4-disilahexane
[0118] ##STR11##
[0119] 116.15 g (0.442 mol) 1,1,1,4,4-pentachloro-1,4-disilabutane
was added to a 250 ml vessel followed by 100 .mu.l
H.sub.2PtCl.sub.6/IPA solution. Solution was heated up to
85.degree. C. and 85.80 g (0.442 mol) pentafluorostyrene was added
slowly during 30 min. After addition solution was stirred for an
hour at 100.degree. C. and then distilled. Bp. 122.degree. C./<1
mbar, yield 158.50 g (78%).
Example 10
1,1,1,4,4-Pentachloro-1,4-disila-5-hexene
[0120] ##STR12##
[0121] 40.00 g (0.152 mol) 1,1,1,4,4-pentachloro-1,4-disilabutane
was dissolved in 1000 ml 1,4-dioxane in a 2000 ml vessel. The
solution was cooled down to 0.degree. C. and acetylene was bubbled
to solution until it was saturated. The solution thus obtained was
slowly warmed up to room temperature. 1,4-dioxane was evaporated
and obtained crude 1,1,1,4,4-pentachloro-1,4-disila-5-hexene was
purified by distillation.
Example 11
1,1,1,4,4-Pentachloro-7-(3,5-dimethyladamantyl)-1,4-disilaheptane
[0122] ##STR13##
[0123] 81.71 g (0.336 mol) 3,5-dimethyladamantylbromide was
dissolved in 500 ml pentane. The solution was cooled to below
-10.degree. C. by ice/acetone bath. 51.40 g (0.425 mol)
allylbromide was added followed by 410 mg FeBr.sub.3. The solution
was then stirred for three hours at -20 . . . 10.degree. C. after
which analysis by GC-MS was carried out, indicating that some
unreacted starting materials remained. 420 mg FeBr.sub.3 was added
and solution was stirred for an additional two hours after which
GC-MS showed that all the dimethyladamantyl bromide had reacted.
The solution was warmed up to room temperature and it was washed
twice with 500 ml water. The organic layer was collected and
pentane was evaporated. Remaining material was dissolved to 700 ml
ethanol and a small amount of water was added followed by 25 g
(0.382 mol) metallic zinc. The solution was then heated up to
reflux and it was stirred for 15 h. After cooling down to room
temperature the solution was filtered. 300 ml water was added and
the product was extracted by washing twice with 500 ml pentane.
Pentane layers were collected and washed once with water. The
organic layer were collected, dried with anhydrous magnesium
sulfate and filtered. Pentane was evaporated and remaining crude
1-allyl-3,5-dimethyladamantane was purified by distillation, yield
45.90 g (67%). 1-allyl-3,5-dimethyladamantane was moved to a 100 ml
vessel followed by 50 .mu.l H.sub.2PtCl.sub.6/IPA solution. The
solution was heated up to 85.degree. C. and 59.50 g (0.227 mol)
1,1,1,4,4-pentachloro-1,4-disilabutane was added slowly during 30
min. After addition, the solution was heated up to 100.degree. C.
and it was stirred for an hour. The product thus obtained was then
purified by distillation yielding 53.54 g (51%), bp.
157-158.degree. C./<0.5 mbar.
Example 12
1,1,1,4,4-Pentachloro-5,6-dimethyl-1,4-disila-6-heptene
[0124] ##STR14##
[0125] 49.85 g (0.190 mol) 1,1,1,4,4-pentachloro-1,4-disilabutane
was added to a 100 ml vessel followed by .about.20-30 mg
tetrakis(triphenylphosphine)palladium(0). The solution was heated
to 80.degree. C. and 13.10 g (0.192 mol) iso-prene was added slowly
during 30 min. After addition, the solution was stirred for an hour
at 100.degree. C. and then distilled. Bp. 96.degree. C./<1 mbar,
yield 58.50 g (93%).
[0126] If the same reaction is carried out with a
H.sub.2PtCl.sub.6/IPA catalyst at 80.degree. C. or with a
Co.sub.2(CO).sub.8 catalyst at room temperature a 1:1 mixture of
.alpha. and .beta. substituted isomers is obtained.
Example 13
1,1,1,4,4-Pentachloro-6-(5-norborn-2-ene)-1,4-disilahexane
[0127] ##STR15##
[0128] 22.63 g (0.086 mol) 1,1,1,4,4-pentachloro-1,4-disilabutane
was added to a 100 ml vessel followed by 70 .mu.l of a
H.sub.2PtCl.sub.6/IPA solution. The solution obtained was heated to
85.degree. C. and 10.81 g (0.090 mol) 5-vinyl-2-norbornene was then
slowly added during 30 min. After addition, the solution was
stirred for an hour at 100.degree. C. and then distilled. Bp.
140.degree. C./<1 mbar, yield 20.05 g (61%).
Example 14
1-(9-Phenanthrenyl)-1,1,4,4,4-pentamethoxy-1,4-disilabutane
[0129] ##STR16##
[0130] 7.23 g (0.297 mol) magnesium and a small amount of iodine
were added to a 1000 ml vessel followed by 56.38 g (0.219 mol)
9-bromophenanthrene. Bis(trimethoxysilyl)ethane (237 g, 0.876 mol)
was added to the vessel, followed by 200 ml THF. In a few minutes,
an exothermic reaction occurred. After the solution had cooled down
it was heated up to reflux and was stirred for over night.
[0131] Refluxing was stopped and 300 ml n-heptane was added.
Solution was decanted to an another vessel and remaining solid was
washed twice with 200 ml n-heptane. The washing solutions were
added to reaction solution. THF and n-heptane were evaporated, and
the remaining material was distilled. B.p. 190-205.degree.
C./<0.1 mbar. Yield was 59.23 g=65%.
Example 15
Dielectric Polymer
[0132] The above described monomers can be polymerized via various
hydrolysis and condensation polymerization methods known in the art
and are thus not limiting factors in course of this invention.
Typical hydrolysis and condensation routes contain organic solvent
or solvent "cocktails" and water as a hydrolysis compound. Also
acids and bases are often used as a catalysts during the synthesis.
The polymer can be polymerized up to various molecular weights
ranging from oligomeric polymers to polymers having molecular
weight of several million g/mol.
[0133] One typical dielectric polymer can be obtained as
follows:
[0134] A solution of
1-(trichlorosilyl)-2-(methyldichlorosilyl)-ethane (20.7 g, 75
mmol),
1-(trichlorosilyl)-2-([3'-{3'',5''-dimethyladamantyl}-propyl]-dichlorosil-
yl)-ethane (11.0 g, 24 mmol) and 130 mL MTBE was dripped into a
well-stirred solution of 130 mL distilled water and 130 mL MTBE at
-2.degree. C. during 40 minutes. After the addition was complete,
the solution was allowed to warm to +13.degree. C. in one hour. The
water layer was discarded and the organic layer was washed with
distilled water until neutral (5.times.30 mL). After filtration
through a 0.45 .mu. glass fibre filter, all volatiles were removed
under reduced pressure, and 21 g polymer was obtained. This was
then dissolved in 85 g MTBE and 260 mg TEA, and was then refluxed
for two hours. After cooling, the solution was washed once with 30
mL 2 w-% HCl, followed by three rinses with 30 mL of distilled
water. Evaporation under reduced pressure gave 20.5 g of a white
powder, that had Mw/Mn=6,300/4,100. It was dissolved in 61.35 g
PGMEA and then spin coated on a silicon wafer.
[0135] Soft bake at 150.degree. C./5 minutes, followed by cure at
450.degree. C. for five hours in N.sub.2 gave a film with
dielectric constant k=2.3. Alternatively, the film was baked after
spin coating at 150.degree. C./5 minutes and then exposed to UV
cure at 350.degree. C. for five minutes and resulted in dielectric
constant k=2.2. In both cases a reactivity of dimethyl adamantyl
was confirmed by FTIR. The FTIR analysis also showed that the films
made via both curing methods were free of silanols.
* * * * *