U.S. patent application number 11/451617 was filed with the patent office on 2006-12-28 for silane monomers and siloxane polymers for semiconductor optoelectronics.
Invention is credited to Jyri Paulasaari, Jarkko Pietikainen, Juha T. Rantala.
Application Number | 20060293478 11/451617 |
Document ID | / |
Family ID | 37025000 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060293478 |
Kind Code |
A1 |
Rantala; Juha T. ; et
al. |
December 28, 2006 |
Silane monomers and siloxane polymers for semiconductor
optoelectronics
Abstract
A method for producing a polymer for semiconductor
optoelectronics, comprising the steps of providing a monomer is
produced having the formula: ##STR1## wherein: R.sub.1 is a
hydrolysable group R.sub.2 is hydrogen, and R.sub.3 is a bridging
linear or branched bivalent hydrocarbyl group, said monomer being
produced by hydrosilylation of the corresponding starting
materials, and homo- or copolymerizing the monomer to produce a
polymer.
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.: |
11/451617 |
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: |
528/15 ;
528/33 |
Current CPC
Class: |
C09D 183/04 20130101;
Y10T 428/31663 20150401; C08G 77/50 20130101; C09D 183/14 20130101;
H01L 21/3127 20130101; C08G 77/08 20130101; H01L 21/02282 20130101;
H01B 3/46 20130101; H01L 21/3122 20130101; H01L 21/02216 20130101;
H01L 21/02126 20130101 |
Class at
Publication: |
528/015 ;
528/033 |
International
Class: |
C08G 77/04 20060101
C08G077/04; C08G 77/08 20060101 C08G077/08 |
Claims
1. A method for producing a polymer for semiconductor
optoelectronics, comprising the steps of providing a monomer is
produced having the formula: ##STR20## wherein: R.sub.1 is a
hydrolysable group R.sub.2 is hydrogen, and R.sub.3 is a bridging
linear or branched bivalent hydrocarbyl group, said monomer being
produced by hydrosilylation of the corresponding starting
materials, and homo- or copolymerizing the monomer to produce a
polymer.
2. The method according to claim 1, wherein hydrosilylation is
carried out in the presence of cobalt octacarbonyl as a
catalyst.
3. The method according to claim 1 or 2, wherein halosilanes are
used as reactants.
4. The method according to any of claims 1 to 3, wherein, for
producing a compound of the formula above, in which R.sub.2 stands
for hydrogen, a first trihalogenated silane compound is reacted
with a second dihalogenated silane compound in the present of
cobalt octacarbonyl.
5. The method according to claim 4, wherein the trihalosilane has a
reactive organic group comprising an unsaturated bond for
facilitating the hydrosilylation reaction.
6. A method of producing a thin film for optoelectronics comprising
depositing on a semiconductor substrate a film obtainable by
polymerization of an organo functionalized monomer having the
formula: ##STR21## wherein: R.sub.1 is a hydrolysable group R.sub.2
is hydrogen, and R.sub.3 is a bridging linear or branched bivalent
hydrocarbyl group, applying the polymerized compositions on a
substrate in the form of a layer and by curing the layer to form a
film.
7. The method according to claim 6, wherein a thin film is produced
from a monomer of the above formula, 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.
8. The method according to claim 6 or 7, wherein the polymerized
composition comprises a cross-linked poly(organosiloxane).
9. The method according thin film according to any of claims 6 to
8, wherein the composition is obtained essentially by
homopolymerization of monomers having formula I.
10. The method according to any of claims 6 to 8, 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.
11. The method according to any of claims 6 to 10, comprising
producing 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 um.
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 fuictionalized 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 finally 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] The commercial use of electronic image sensors in
electronics and, in particular in consumer electronics, has
increased dramatically over the last few years. Electronic image
sensors are found in cameras, cell phones, and are used for new
safety features in automobiles e.g. for estimating distances
between vehicles, protecting and detecting blind spots not exposed
by mirrors etc. Many semiconductor manufacturers are converting
production lines to CMOS sensor production to meet this demand.
CMOS sensor manufacturing uses many of the processes currently used
in standard IC manufacturing and does not require large capital
investment to produce state of the art devices.
[0006] Processing from the bottom up a photodiode is built in the
silicon layer. Standard dielectrics and metal circuitry are built
above the diode to transfer the current. Directly above the diode
is an optically transparent material to transfer light from the
device surface and through a color filter to the active
photo-diode. Transparent protection and planarization material is
typically placed over the color filters and device. The
micro-lenses are built over the planarized layer above the color
filters in order to improve device performance. Finally a
passivation layer maybe placed over the lens or alternatively a
glass slide is placed over the lens array leaving an air gap
between the lens and the cover. Most CMOS sensors are built using
subtractive aluminum/CVD oxide metallization with one or more
levels of metal. For the manufacturing of planarizing layer or
micro-lenses are also used organic polymers such as polyimide or
novolac materials or maybe sometimes siloxane polymers.
[0007] 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. For example, organic polymer cannot be chemical
mechanical polished or etched back by dry processing without
damaging the film.
[0008] Therefore some of recent focus has been on SSQ
(silsesquioxane or siloxane) or silica based dielectric and optical
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.
[0009] 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.
However, these films index of refraction at visible range typically
around 1.4 to 1.5 and always less than 1.6.
[0010] 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.
SUMMARY OF THE INVENTION
[0011] It is an object of the present invention to provide a novel
high index of refraction siloxane polymer compatible with
traditional Integrated Circuit (IC) processing and CMOS image
sensor applications.
[0012] It is another object to provide a method of modifying the
monomer so as to form a novel organo-functionalized molecule.
[0013] 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 and optical properties.
[0014] 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.
[0015] It is a fifth object of the invention to provide dielectric
layers on silicon and glass wafers.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] The general formula I of the precursor used in the present
invention is the following: ##STR2## wherein: [0021] R.sub.1 is a
hydrolysable group, such as hydrogen, a halide, an alkoxy or an
acyloxy group, [0022] R.sub.2 is hydrogen, an organic crosslinking
group, a reactive cleaving group or a polarizability reducing
organic group, and [0023] R.sub.3 is a bridging linear or branched
bivalent hydrocarbyl group.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] The new material can be used as an optical dielectric film
in an object comprising e.g. a (silicon) wafer.
[0028] The present invention also provides a method of forming a
thin film having a dielectric constant of 4.0 or less or more
preferably 3.5 or less and index of refraction more than 1.58 or
preferably more than 1.60 at 632.8 nm wavelength range, 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.
[0029] 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 optical dielectric polymers, more specifically index of
refraction, CMP compatibility, mechanical properties (modulus and
hardness), cracking threshold and thermal properties, also
applicable to IC integration 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.
[0030] 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.
[0031] The present invention provides excellent chemical resistance
and very low chemical adsorption behavior due to high cross-linking
bridging group density.
[0032] 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.
[0033] Another important advantages is that the novel optical
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.
[0034] Furthermore, the novel materials have excellent gap fill
properties.
[0035] In summary, the present invention provides an optical
dielectric siloxane polymer applicable to forming thermally and
mechanically stable, high index of refraction, 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 and optical 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 optical dielectric polymers, are crucial
to overcome existing problems as well as in order to improve device
performance in optical dielectric film integration to a optical
semiconductor device.
[0036] Next, the invention will be examined more closely by means
of the following detailed description and with reference to a
number of working examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 shows a schematic cross-section of CMOS image sensor
device;
[0038] FIG. 2 shows the thermogravimetric diagram of high index of
refraction Polymer 3; and
[0039] FIG. 3 shows a thermogravimetric diagram of high index of
refraction Polymer 4.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The present invention provides an optical dielectric 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, index of refraction increasing group, UV
blocking group, polarizability reducing organic group or a
combination of all previous such as an alkyl, alkenyl, alkynyl,
aryl, polyaromatic, polycyclic group or organic containing silicon
group.
[0041] 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, methoxide or ethoxide groups or any
of their combination.
[0042] The general formula I of the precursor used for
polymerization in the present invention is the following: ##STR3##
wherein: [0043] R.sub.1 is a hydrolysable group [0044] 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 [0045] R.sub.3 is a
bridging linear or branched bivalent hydrocarbyl group.
[0046] 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, and bivalent
alicyclic groups (polycyclic groups) and bivalent aromatic groups
which all are included in the definition of a bivalent hydrocarbyl
group.
[0047] 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.
[0048] `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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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)
[0054] 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.
[0055] "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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] As mentioned above, in a first step of the method according
to the present invention, a monomer is produced having the formula:
##STR4## wherein: [0063] R.sub.1 is a hydrolysable group [0064]
R.sub.2 is hydrogen, and [0065] R.sub.3 is a bridging linear or
branched bivalent hydrocarbyl group.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] The present invention provides an optical dielectric
siloxane polymer applicable for forming thermally and mechanically
stable, high index of refraction, optically transparent, 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.
[0071] 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.
[0072] 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.
[0073] 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. Furthermore, the monomers of
formula I can be also co-polymerized with any know hydrolysable
siloxane or organo-metallic (e.g. titanium alkoxide, titanium
chloride, zirconium alkoxide, zirconium chloride, tantalum
alkoxide, tantalum chloride, aluminum alkoxide or aluminum chloride
but not limited to these) monomer in any ratio.
[0074] 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.
[0075] 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.
[0076] The polymer of the present invention is capable of forming
low dielectric films having a dielectric constant of 4.0 or less,
in particular 3.5 or less, index of refraction 1.58 or more, in
particular 1.60 or more at 632.8nm wavelength range, a Young's
modulus of 5.0 GPa or more, a porosity of 5% or less and cracking
threshold of 1 um 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
400.degree. C. or more.
[0077] As mentioned above, the present invention also provides
methods of producing integrated circuit devices. Such methods
typically comprise the steps of: [0078] forming a plurality of
transistors on a semiconductor substrate; [0079] forming multilayer
interconnects by: [0080] depositing a layer of metal; [0081]
patterning the metal layer; [0082] depositing a first dielectric
material having a first modulus and a first k value; [0083]
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
[0084] patterning the first and second dielectric materials and
depositing a via filling metal material into the patterned
areas.
[0085] 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:
[0086] a k value of 4.0 or less or even more preferably 3.5 or
less, [0087] an index of refraction of 1.58 or more or even more
preferably 1.6 or more [0088] a CTE 30 ppm or less, and [0089]
Young's modulus 4 GPa or more.
[0090] 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.
[0091] 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.
[0092] Alternatively, the organosiloxane material can be deposited
by polymerizing a monomer of formula I with any know hydrolysable
siloxane or organo-metallic (e.g. titanium alkoxide, titanium
chloride, zirconium alkoxide, zirconium chloride, tantalum
alkoxide, tantalum chloride, aluminum alkoxide or aluminum chloride
but not limited to these) monomer in a liquid medium formed by a
first solvent to form a hydrolyzed product comprising a siloxane
material or hybrid siloxane-organo-metallic 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.
[0093] 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.
[0094] Generally, the organosiloxane material is a spin coated
material.
[0095] The organosiloxane material is an organic-inorganic and has
a coefficient of thermal expansion of 12 to 30 ppm. It can have an
index of refraction of 1.6 or less.
[0096] 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)
[0097] ##STR5##
[0098] 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
[0099] ##STR6##
[0100] 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
[0101] ##STR7##
[0102] 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
[0103] ##STR8##
[0104] 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
[0105] ##STR9##
[0106] 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%).
[0107] 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
[0108] ##STR10##
[0109] 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
[0110] ##STR11##
[0111] 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 (0.442mol) 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
[0112] ##STR12##
[0113] 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
[0114] ##STR13##
[0115] 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
[0116] ##STR14##
[0117] 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%).
[0118] 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
[0119] ##STR15##
[0120] 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
9-Phenanthrenyl triethoxysilane
[0121] ##STR16##
[0122] 5.33 g (0.219 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. 196 ml (182.74 g, 0.877 mol) Si(OEt).sub.4 was
added to the vessel. 200 ml THF was added after which exothermic
reaction occurred. After the solution had cooled down it was heated
up to reflux and was stirred for over night.
[0123] 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. 175.degree. C./0.7 mbar.
Yield was 52.63 g=70%.
Example 15
1-(9-Phenanthrenyl)-1,1,4,4,4-pentamethoxy-1,4-disilabutane
[0124] ##STR17##
[0125] 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.
[0126] 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 16
3-(9-Phenanthrenyl)propyl trimethoxysilane
[0127] ##STR18## ##STR19##
[0128] 6.90 g (0.284 mol) magnesium powder and a few crystals of
iodine were added to a 1000 ml vessel followed by 73.07 g (0.284
mol) 9-bromophenanthrene. 90 ml THF was added after which
exothermic reaction occurred. While the solution had cooled down
back to room temperature 30 ml THF was added and the solution was
heated up to 65.degree. C. and stirred for over night.
[0129] Solution was allowed to cool down to 50.degree. C. and 34.42
g (0.285 mol) allylbromide was added dropwice during 30 min at a
rate that kept solution gently refluxing. After addition solution
was stirred for 2 hours at 65.degree. C. Solution was cooled down
to room temperature and most of THF was removed by vacuum. 700 ml
DCM was added and solution moved to separation funnel. Solution was
washed twice with 700 ml water. Organic layer was collected and
dried with anhydrous magnesium sulfate. Solution was filtered
followed by evaporation of solvents. Remained material was purified
by distillation. B.p. 110-115.degree. C./<0.5 mbar. Yield 54.5 g
(88%).
[0130] Allylphenanthrene (41.59 g, 0.191 mol) was added to a 250 ml
round bottomed flask and heated up to 90.degree. C. 50 .mu.l 10%
H.sub.2PtCl.sub.6 in IPA was added. Addition of HSiCl.sub.3 was
started and exothermic reaction was observed. 26.59 g (0.196 mol)
HSiCl.sub.3 was added slowly during 40 min. After addition solution
was stirred for an hour at 100.degree. C. Excess HSiCl.sub.3 was
removed by vacuum and 100 ml (97 g, 0.914 mol) trimethyl
orthoformate was added followed by 50 mg Bu.sub.4PCl as a catalyst.
Solution was stirred for 90 hours at 70.degree. C. and product was
purified by distillation. B.p. 172.degree. C./<0.5 mbar. Yield
50 g (74% based on amount of allylphenanthrene).
Example 17
High Index of Refraction Polymer 1
[0131] 9-Phenanthrenyl triethoxysilane (15 g, 44 mmol), acetone
(22.5 g) and 0.01M HCl (7.2 g, 400 mmol) were placed in a 100 mL rb
flask and refluxed for 23 hours. The volatiles were evaporated
under reduced pressure. White solid polymer (11.84 g) was obtained.
The polymer was diluted in PGMEA (29.6 g, 250%) and then casted on
a silicon wafer. Soft bake 150.degree. C./5 min, followed by cure
at 400.degree. C./15 min. The index of refraction was 1.6680 at
632.8 nm wavelength range and dielectric constant 3.5 at 1 MHz.
However, polymer did not have excellent chemical resistance against
standard organic solvent and alkaline wet etch chemicals.
Example 18
High Index of Refraction Polymer 2
[0132] 9-Phenanthrenyltriethoxysilane (17.00 g, 0.05 mol, prepared
by Grignard reaction between 9-bromophenanthrene, magnesium, and
tetraethoxysilane in THF) and acetone (15.00 g) were stirred until
solids dissolved. Dilute nitric acid (0.01M HNO.sub.3, 6.77 g, 0.38
mol) was then added. Two phases (water and organic) separated. The
system was refluxed until the solution became clear (.about.15
min). Glycidyloxypropyltrimethoxysilane (3.00 g, 0.01) was added
and the flask was refluxed for six hours. Volatiles were evaporated
in rotary evaporator until 25.00 g polymer solution remained.
N-Propyl acetate (32.50 g) was added and evaporation continued
again until 27 g remained. Next, propylene glycol monomethyl ether
acetate (30 g) was added and again evaporated until 24.84 g was
left as viscous polymer. Amount of non-volatiles was measured to be
69.24%. More PGMEA (8.89 g) was added so that solid content was
.about.50%. The solution was heated in oil bath (165.degree. C.)
and refluxed for 4 hours 20 minutes. The water that formed during
the reaction was removed in rotary evaporator, along with PGMEA
until 18 g remained. More PGMEA (42 g) was added to give solution
with solid content 22.16%. Polymer had M.sub.n/M.sub.w=1,953/2,080
g/mol, as measured by GPC against monodisperse polystyrene
standards in THF.
[0133] Sample preparation: The solution above (9.67 g) was
formulated with PGMEA (5.33 g), surfactant (BYK-307 from
BYK-Chemie, 4 mg) and cationic initiator (Rhodorsil 2074, 10 mg).
It was spin-coated on a 4'' wafer at 2,000 rpm. The film was soft
baked at 130.degree. C./5 mins and cured at 200.degree. C./5 mins.
Film thickness after cure was 310 nm and index of refraction of
1.66 at 632.8 nm and dielectric constant 3.4 at 1 MHz. The film did
not dissolve with acetone, indicating that cross-linking had been
successful. Similarly, a more concentrated PGMEA solution (solids
25%) was prepared, spun and cured. The film was 830 nm thick and
had modulus 7.01 GPa and hardness 0.41 GPa as measured by
nanoindentation.
Example 19
High Index of Refraction Polymer 3
[0134] 1-(9-Phenanthrenyl)-1,1,4,4,4-pentamethoxy-1,4-disilabutane
(9.55 g, 22.9 mmol), 9-Phenanthrenyl triethoxysilane (9.02 g, 26.5
mmol) and SLSI-grade acetone (14.0 g) were placed in a 250 ml rb
flask with a teflon coated magnetic stir bar. Distilled water (6.0
g, 333 mmol) was added and system was refluxed for 15 mins. Then, 2
drops of dil.HCl (3.7 w-% was dripped in. In two minutes the
solution became homogenous, indicating the progress of hydrolysis.
A solution of
1-(9-Phenanthrenyl)-1,1,4,4,4-pentamethoxy-1,4-disilabutane (11.45
g, 27.5 mmol) in acetone (16.0 g) was poured in, followed by 0.01M
HCl solution (8.4 g, 466 mmol). The reaction was allowed to reflux
for 14 hours. After the reflux, all volatiles were removed under
vacuum, yielding 28.1 g dry polymer as clear colorless solids. It
was thermally stable up to 500.degree. C. in argon atmosphere,
measured by TGA (FIG. 2.).
[0135] The solids were diluted in n-butyl acetate (NBA, 73.06 g,
260%) and surfactant (56 mg, BYK.RTM.-307 of Byk-Chemie).
Alternatively, solutions in propylene glycol mono methyl ether
acetate (PGMEA, 240%) and methyl ethyl ketone (MEK, 400%) were also
prepared. The solution in NBA was filtered through a 0.2 .mu.
teflon filter, and spin casted on a 4'' silicon wafer at 3000 rpm.
Soft bake at 150.degree. C./5 mins and 200.degree. C./5 mins,
followed by the cure at 400.degree. C./15 mins in N.sub.2 ambient
gave film with index of refraction 1.6511 at 632.8 nm and thickness
of 683 nm. The dielectric constant of the film was 3.4 at 1 MHz.
Films with final thicknesses up to 1850 nm were prepared, and they
showed no sign of cracking. The film could be rubbed with organic
solvents such as acetone without damaging it.
Example 20
High Index of Refraction Polymer 4
[0136] 3-(9-Phenanthrenyl)propyl trimethoxysilane (11.0 g, mmol)
acetone (16.5 g) and 0.01M HCl were placed in a 100 ml rb flask and
refluxed for 16 hours. At the beginning, the solution was milky
white, but became clear soon after the hydrolysis started. When the
polymerization further progressed, the solution turned again
slightly cloudy. The volatiles were removed by evaporation under
reduced pressure, giving white colorless powder 9.60 g. The polymer
was stable up to 450.degree. C. under argon, measured by TGA (FIG.
3.).
[0137] The casting solution was prepared by dissolving 2.06 g
polymer in 8.24 g methyl ethyl ketone (400%) and a surfactant (5
mg, BYK.RTM.-307 of Byk-Chemie), and filtered through 0.2 .mu.
Teflon filter. The polymer was spin casted on a 4'' silicon wafer
at 3000 rpm. Soft bake at 150.degree. C./5 mins, followed by the
cure at 400.degree. C./15 mins in N.sub.2 ambient gave a film with
index of refraction 1.671 at 632.8 nm and thickness of 840 nm. The
dielectric constant of the film was 3.4 at 1 MHz. The film showed
no sign of cracking. The film could be rubbed with organic solvents
such as acetone without damaging it.
[0138] All high index of refraction polymers were also tested for
trench gap-fill with trenches 1 .mu.m (width).times.4 um (height).
All polymers showed excellent gap-fill performance and showed no
cracking after 400.degree. C./15 mins in N.sub.2 ambient.
[0139] It was also found out that all high index of refraction
polymers 1-4 that are compatible with CMP (chemical mechanical
polishing). It was found advantageous that cure films first at 150
to 300.degree. C. prior performing CMP with traditional oxide CMP
slurry and then applying additional higher temperature cure at 180
to 450.degree. C. When first cured at lower temperature the film
gets only partially cured, i.e., some residual silanols remains in
the film. Due to silanols the polymer films is still slightly
hydrophilic, which preferable when performing oxide CMP process.
All polymers were also compatible with etch back process by using
oxygen plasma. The polymer film etched very uniformly about 100 mm
per minute when applying oxygen plasma and the plasma process did
not cause any index of reaction shift, surface roughness increase
or defect formation. It is worth notifying that conventional high
index of refraction organic polymers cannot be CMP and etch back
processed without damaging the film surface quality or changing the
film optical properties.
[0140] There are also three important technical issues for new
generations of CMOS image sensors (FIG. 1) that can be reached with
above-mentioned chemistries: size of the device; speed and power
consumption; quantum efficiency.
[0141] Explanation of FIG. 1: 10 semiconductor substrate; 20
photo-diode; 30 metal lines, interlayer dielectrics and intermetal
dielectrics; 40 colour filter array layer; 50 micro-lens array; 100
high aspect ratio photo-diode gap filled with high index of
refraction siloxane polymer; 200 high index of refraction siloxane
polymer for color filter planarization and passivation and; 300
micro-lens passivation siloxane polymer.
[0142] Size of the device: the smaller the pixel the greater the
number of pixels on same area, i.e., improved field factor. This is
can be achieved by reducing lens size, diode size, thinner
metallization and applying multiple levels of metal.
[0143] Speed: shortening the metal lines, improving the conductor
Cu versus Al and lowering the k value of the dielectric will
improve speed and reduce power consumption.
[0144] Quantum efficiency: this is an opportunity to improve the
device efficiency by using new materials that bring light into the
lens and transmit light down to the diodes.
[0145] Materials deposited before the color filter array and be
cured at relatively high temperatures to lock in their mechanical
properties and being compatible with other materials used in chip
construction. Materials deposited after the color filters are
deposited must be fully cured at lower temperatures ca 250.degree.
C. or below. Materials of this invention are highly suitable for
applications above and below the color filter array.
[0146] Maximizing quantum efficiency: Light incident on the lens is
focused and passes through the color filter and is transmitted down
to the diode in the device layer. The objective is to maximize the
amount of light reaching the diode. For example the material
immediately above the diode needs to be transparent and transmit
the maximum amount of light. The interface of the sidewalls of
material 100 at FIG. 1 is a source of light loss due to refraction
and reduces the light reflected down into the diode. A simple
solution is to line the sidewall with a reflective coating but that
would add expense and would be very difficult. Also CVD metal
deposition will make the channel narrower (reducing light
transmission) and eventually pinch off at the top for narrow
features. However if material 100 has a higher index of refraction
than the material used to make the wall next to it then refraction
will be minimized and more light will be guided down to the diode.
Thus the metallization is surrounded by CVD SiO.sub.2 which forms
the sidewall for the light channel. CVD oxide has an index of
refraction approx of 1.46 at 632.8 nm wavelength range and so the
light channel needs to have refractive index >1.46 to reduce
refraction at the interface. Thus basically this is a vertical
waveguide transmitting light to the diode. Thus a polymer from
Example 19 based material with high index of refraction would
function well for this application. This is a transparent film and
thus would be mechanically compatible with the neighboring CVD
SiO.sub.2. The index of refraction of polymer from Example 19 is
1.65 and thus would increase the reflectivity of the light from the
oxide sidewalls with refractive index of 1.46. While this material
can be cured at low temperatures of 250.degree. C., it can also be
cured at higher temperatures above 400.degree. C. to be compatible
with processes required with Al, Cu and SiO.sub.2. Furthermore as
devices are made smaller and metallization shortened to improve
speed, the aspect ratio for the channel increases.
[0147] Passivation of the Color Filters and the Lenses: The
material (200 in FIG. 1) above the color filter array is another
opportunity for an inexpensive enhancement for device performance.
A polymer from Example 18 is transparent to visible light yet
effectively blocks UV thus light protecting both the color filter
and the diode as well as signal noise. Also the polymer from
Example 18 is an excellent planarizing material and an effective
passivation layer. The polymer also matches the index of
refractions between color filter layer and micro-lens layer, thus
reduces reflection from the film interfaces. Also this material can
be cured at low temperatures .about.200.degree. C. and therefore
does not cause thermal degradation to organic color filter
materials.
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