U.S. patent application number 09/803520 was filed with the patent office on 2001-07-26 for process for forming an integrated circuit.
Invention is credited to Carter, Kenneth R., Hedrick, James L., Lee, Victor Yee-Way, McHerron, Dale C., Miller, Robert D..
Application Number | 20010009296 09/803520 |
Document ID | / |
Family ID | 23289083 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009296 |
Kind Code |
A1 |
Carter, Kenneth R. ; et
al. |
July 26, 2001 |
Process for forming an integrated circuit
Abstract
A novel dielectric composition is provided that is useful in the
manufacture of integrated circuit devices and integrated circuit
packaging devices. The dielectric composition is prepared by
imidizing and curing an oligomeric precursor compound comprised of
a central polybenzoxazole, polybenzothiazole, polyamic acid or
polyamic acid ester segment end-capped at each terminus with an
aryl-substituted acetylene moiety such as an
ortho-bis(arylethynyl)aryl group, e.g.,
3,4-bis(phenylethynyl)phenyl. Integrated circuit devices,
integrated circuit packaging devices, and methods of synthesis and
manufacture are provided as well.
Inventors: |
Carter, Kenneth R.; (San
Jose, CA) ; Hedrick, James L.; (Pleasanton, CA)
; Lee, Victor Yee-Way; (San Jose, CA) ; McHerron,
Dale C.; (Staatsburg, NY) ; Miller, Robert D.;
(San Jose, CA) |
Correspondence
Address: |
Dianne E. Reed
REED & ASSOCIATES
3282 Alpine Road
Portola Valley
CA
94028
US
|
Family ID: |
23289083 |
Appl. No.: |
09/803520 |
Filed: |
March 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09803520 |
Mar 8, 2001 |
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09330285 |
Jun 11, 1999 |
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Current U.S.
Class: |
257/642 ; 257/40;
257/638; 257/643; 257/759; 257/774; 257/E21.259; 257/E21.589;
257/E23.167; 438/623; 438/629; 438/637; 438/639; 438/725; 438/780;
438/82 |
Current CPC
Class: |
H01L 21/02118 20130101;
H01L 21/02282 20130101; H01L 21/02205 20130101; H01L 2924/0002
20130101; H01L 21/76885 20130101; H01L 21/312 20130101; H05K 1/0306
20130101; H01L 23/5329 20130101; H01L 2924/09701 20130101; H05K
3/285 20130101; H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/642 ; 257/40;
257/638; 257/643; 257/759; 257/774; 438/82; 438/725; 438/780;
438/623; 438/629; 438/637; 438/639 |
International
Class: |
H01L 035/24; H01L
051/00; H01L 021/00; H01L 021/4763; H01L 023/52; H01L 023/48; H01L
029/40; H01L 023/58 |
Claims
1. An oligomeric compound useful for preparing a dielectric
composition, the compound having the structural formula (I)
10wherein: n is an integer of 2 or more; q is 0 or 1; R is an
oligomeric unit comprised of polybenzoxazole, polybenzothiazole,
polyamic acid or a polyamic acid ester; R.sup.1 is an aromatic
group optionally substituted at one or more available carbon atoms
with an inert, nonhydrogen substituent; L is a linking group; and
Ar is arylene optionally substituted at one or more available
carbon atoms with an inert, nonhydrogen substituent:
2. The oligomeric compound of claim 1, wherein: n is 2; and q is
0.
3. The oligomeric compound of claim 2, wherein R is a polyamic acid
ester.
4. The oligomeric compound of claim 3, wherein R comprises the
reaction product of: (a) a diamine; and (b) a diester diacyl halide
formed from reaction of a tetracarboxylic dianhydride with a lower
alkanol and a halogenating reagent.
5. The oligomeric compound of claim 4, wherein: the diamine has the
structural formula H.sub.2N--R.sup.2--NH.sub.2 in which R.sup.2 is
a difunctional monocyclic or bicyclic aromatic moiety; and the
tetracarboxylic dianhydride has the structural formula 11wherein Q
is a tetrafunctional monocyclic, bicyclic or tricyclic aromatic
moiety.
6. A process for preparing an oligomeric compound useful as a
precursor useful for preparing a dielectric composition, wherein
the oligomeric compound has the structural formula (I) 12in which:
n is an integer of 2 or more; q is 0 or 1; R is an oligomeric unit
comprised of polybenzoxazole, polybenzothiazole, polyamic acid or a
polyamic acid ester; R.sup.1 is an aromatic group optionally
substituted at one or more available carbon atoms with an inert,
nonhydrogen substituent; L is a linking group; and Ar is arylene
optionally substituted at one or more available carbon atoms with
an inert, nonhydrogen substituent, the process comprising
synthesizing the oligomeric unit R in the presence of a
predetermined quantity of an end-capping moiety
Z--Ar(--C.ident.C--(L).- sub.q--R.sup.1).sub.n, wherein Z is
selected from the group consisting of NH.sub.2, OH, COOH and
halo.
7. The process of claim 6, wherein, wherein: n is 2; and q is
0.
8. The process of claim 7, wherein R is a polyamic acid ester.
9. The process of claim 8, wherein the oligomeric unit R is
synthesized by reaction of a diamine and a diester diacyl halide
formed from reaction of a tetracarboxylic dianhydride with a lower
alkanol and a halogenating reagent.
10. The process of claim 9, wherein the diamine has the structural
formula H.sub.2N--R.sup.2--NH.sub.2 in which R.sup.2 is a
difunctional monocyclic or bicyclic aromatic moiety; the
tetracarboxylic dianhydride has the structural formula 13wherein Q
is a tetrafunctional monocyclic, bicyclic or tricyclic aromatic
moiety; and the halogenating reagent is oxalyl halide.
11. The process of claim 6, wherein the predetermined quantity of
the end-capping moiety is such that the oligomeric compound
synthesized has a number average molecular weight in the range of
approximately 5000 to 20,000 g/mol.
12. A process for preparing a dielectric composition, comprised
heating to a predetermined temperature an oligomeric compound
having the structural formula (I) 14wherein: n is an integer of 2
or more; q is 0 or 1; R is an oligomeric unit comprised of
polybenzoxazole, polybenzothiazole, polyamic acid or a polyamic
acid ester; R.sup.1 is an aromatic group optionally substituted at
one or more available carbon atoms with an inert, nonhydrogen
substituent; L is a linking group; and Ar is arylene optionally
substituted at one or more available carbon atoms with an inert,
nonhydrogen substituent, wherein the predetermined temperature is
sufficient to effect imidization of the oligomeric unit R and
crosslinking of the --C.ident.C--(L).sub.q--R.sup.1 termini.
13. The process of claim 12, wherein: n is 2; and q is 0.
14. The process of claim 13, wherein R is a polyamic acid
ester.
15. The process of claim 14, wherein R comprises the reaction
product of: (a) a diamine; and (b) a diester diacyl halide formed
from reaction of a tetracarboxylic dianhydride with a lower alkanol
and a halogenating reagent.
16. The process of claim 15, wherein: the diamine has the
structural formula H.sub.2N--R.sup.2--NH.sub.2 in which R.sup.2 is
a difunctional monocyclic or bicyclic aromatic moiety; the
tetracarboxylic dianhydride has the structural formula 15wherein Q
is a tetrafunctional monocyclic, bicyclic or tricyclic aromatic
moiety; and the halogenating reagent is an oxalyl halide.
17. The process of claim 12, wherein the predetermined temperature
is at least about 250.degree. C.
18. The process of claim 17, wherein the predetermined temperature
is at least about 400.degree. C.
19. A dielectric composition prepared by the process of claim
12.
20. A dielectric composition prepared by the process of claim
13.
21. A dielectric composition prepared by the process of claim
14.
22. A dielectric composition prepared by the process of claim
15.
23. A dielectric composition prepared by the process of claim
18.
24. An end-capping reagent having the structural formula (II)
16wherein: n is an integer of 2 or more; q is 0 or 1; R.sup.1 is an
aromatic group optionally substituted at one or more available
carbon atoms with an inert, nonhydrogen substituent; L is a linking
group; Ar is arylene optionally substituted at one or more
available carbon atoms with an inert, nonhydrogen substituent; and
Z is selected from the group consisting of NH.sub.2, OH, COOH and
halo.
25. An integrated circuit device comprising: (a) a substrate; (b)
individual metallic circuit lines positioned on the substrate; and
(c) a dielectric composition positioned over and/or between the
individual metallic circuit lines, the dielectric composition
comprising an imidized, cured oligomer precursor compound, the
precursor compound comprised of a polybenzoxazole,
polybenzothiazole, polyamic acid or polyamic acid ester segment
capped at each terminus with a moiety
--Ar(--C.ident.C--(L).sub.q--R.sup.1).sub.n wherein n is an integer
of 2 or more, q is 0 or 1, R represents the polybenzoxazole,
polybenzothiazole, polyamic acid or polyamic acid ester segment,
R.sup.1 is an aromatic group optionally substituted at one or more
available carbon atoms with an inert, nonhydrogen substituent, L is
a linking group, and Ar is arylene optionally substituted at one or
more available carbon atoms with an inert, nonhydrogen
substituent.
26. The device of claim 25, wherein, in the precursor compound, n
is 2 and q is 0.
27. The device of claim 26, wherein R represents a polyamic acid
ester.
28. The device of claim 27, wherein R comprises the reaction
product of: (a) a diamine; and (b) a diester diacyl halide formed
from reaction of a tetracarboxylic dianhydride with a lower alkanol
and a halogenating reagent.
29. The device of claim 28, wherein: the diamine has the structural
formula H.sub.2N--R.sup.2--NH.sub.2 in which R.sup.2 is a
difunctional monocyclic or bicyclic aromatic moiety; the
tetracarboxylic dianhydride has the structural formula 17wherein Q
is a tetrafunctional monocyclic, bicyclic or tricyclic aromatic
moiety; and the halogenating reagent is an oxalyl halide.
30. A process for forming an integrated circuit, comprising: (a)
depositing a metallic film on a substrate; (b) lithographically
patterning the metallic film; (c) depositing the oligomeric
compound of claim 1 onto the lithographically patterned metallic
film; and (d) heating the substrate to a temperature sufficient to
both imidize and crosslink the oligomeric compound.
31. An integrated circuit packaging device for providing signal and
power current to an integrated circuit chip, comprising: (i) a
substrate having electrical conductor means for connection to a
circuit board, (ii) a plurality of alternating electrically
insulating and conducting layers positioned on the substrate
wherein at least one of the layers is comprised of a dielectric
composition comprising an imidized, cured oligomer precursor
compound, the precursor compound comprised of a polybenzoxazole,
polybenzothiazole, polyamic acid or polyamic acid ester segment
capped at each terminus with a moiety --Ar(--C.ident.C--(L).sub.q-
--R.sup.1).sub.n wherein n is an integer of 2 or more, q is 0 or 1,
R represents the polybenzoxazole, polybenzothiazole, polyamic acid
or polyamic acid ester segment, R.sup.1 is an aromatic group
optionally substituted at one or more available carbon atoms with
an inert, nonhydrogen substituent, L is a linking group, and Ar is
arylene optionally substituted at one or more available carbon
atoms with an inert, nonhydrogen substituent; and (iii) a plurality
of vias for electrically interconnecting the electrical conductor
means, the conducting layers and the integrated circuit chip.
Description
TECHNICAL FIELD
[0001] This invention relates generally to dielectric materials and
their use in integrated circuits. More particularly, the invention
pertains to novel dielectric polymer compositions, oligomeric
precursors and methods for preparing the compositions, and
integrated circuit devices fabricated therewith.
BACKGROUND
[0002] Polyimides are known in the art for use in the manufacture
of integrated circuits including chips (e.g., chip back end of
line, or "BEOL"), thin film packages, and printed circuit boards.
Polyimides are useful in forming dielectric interlayers,
passivation layers, alpha particle barriers, and stress buffers.
Polyimides are particularly useful as an interlayer dielectric
material to insulate the conductor wiring interconnecting the chips
on a multichip module. This is known as "thin film" wiring.
Multichip modules represent an intermediate level of packaging
between the chips and the circuit board, and are generally known in
the art. Multichip modules are made up of multiple layers of power,
signal, and ground planes which deliver power to the chips and
distribute the input/output signals between chips on the module or
to and from the circuit board.
[0003] There is a continuing desire in the microelectronics
industry to increase the circuit density in multilevel integrated
circuit devices, e.g., memory and logic chips, thereby increasing
performance and reducing cost. In order to accomplish these goals,
those in the field are striving to reduce the minimum feature
sizes, e.g., metal lines and vias, and to decrease the dielectric
constant of the interposed dielectric material to enable closer
spacing of circuit lines without a concomitant increase in
crosstalk and capacitive coupling. Polyimides usually have
dielectric constants of about 3.0-3.8 and mechanical and thermal
properties sufficient to withstand present processing operations
including the thermal cycling associated with semiconductor
manufacturing. However, there is a need in the art for a dielectric
material that would be suitable for use in integrated circuit
devices, wherein the material exhibits a lower dielectric constant
(e.g., <3.0) than typically exhibited by polyimides and has
improved mechanical and thermal properties.
[0004] The invention is addressed to the aforementioned need in the
art, and, in one embodiment, provides a novel dielectric
composition that represents a significant improvement over prior
dielectric materials used in integrated circuit devices. The
composition is formed by imidizing and curing an oligomeric
precursor compound comprised of a central polyamic acid or polyamic
acid ester segment terminated at each end with an aromatic species
substituted with two or more aryl-substituted ethynyl moieties.
These oligomeric compounds, dielectric compositions formed
therefrom, and associated methods of manufacture and use will be
discussed in detail herein.
[0005] Compounds that are end-capped with two or more
diaryl-substituted acetylene moieties at each of two termini are
known and described, for example, in PCT Publication No. WO
97/10193. The reference does not, however, describe end-capped
oligomeric segments comprised of polyamic acid, a polyamic acid
ester, or the like.
[0006] U.S. Pat. No. 5,138,028 to Paul et al. is also of interest
insofar as polyimides end-capped with diaryl-substituted acetylene
are disclosed. Only one diaryl-substituted acetylene moiety is
present at each terminus, resulting in higher curing temperature
and less efficient cross linking than possible with the oligomeric
precursor compounds of the invention.
[0007] John et al. (1994), "Synthesis of Polyphenylenes and
Polynaphthalenes by Thermolysis of Enediynes and
Dialkynylbenzenes," J. Am. Chem. Soc. 116:5011-5012, is of
background interest insofar as the publication describes thermal
polymerization of substituted enediynes. U.S. Pat. No. 5,773,197 to
Carter et al. is also a background reference that is of interest
with respect to the present invention, in that the patent describes
the manufacture and use of integrated circuit devices in which a
dielectric material contained therein is synthesized on a
substrate.
[0008] No art of which applicants are aware, however, describes or
suggests the dielectric compositions as now provided herein, or the
oligomeric precursor compounds that are imidized and crosslinked to
form the compositions. In contrast to the dielectric materials of
the prior art, the present compositions provide the following
advantages: (1) the precursor to the present dielectric
compositions has a lower solution viscosity than other polyimide
precursors, allowing for superior planarization and gap filling;
(2) the present dielectric compositions have a low dielectric
constant, less than 3.0, which is lower than that of currently used
dielectric materials; and (3) films of the novel dielectric
compositions have superior mechanical properties relative to
current dielectric materials used in the manufacture of integrated
circuit devices and packages. The compositions also find utility in
laminates, composites and the like.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is a primary object of the invention to
address the above-mentioned need in the art by providing novel
dielectric materials that are useful, inter alia, in integrated
circuit devices.
[0010] It is another object of the invention to provide oligomeric
precursor compounds useful for preparing the novel dielectric
compositions.
[0011] It is still another object of the invention to provide such
oligomeric precursor compounds comprised of a central oligomeric
segment end-capped at each of two termini with an aryl-substituted
acetylene moiety such as an ortho-bis(arylethynyl)aryl group.
[0012] It is yet another object of the invention to provide such
oligomeric precursor compounds wherein the central oligomeric
segment is a polyamic acid, a polyamic acid ester, a
polybenzoxazole, or a polybenzothiazole.
[0013] It is a further object of the invention to provide methods
for synthesizing the oligomeric precursor compounds and methods for
preparing the novel dielectric compositions therefrom.
[0014] It is still a further object of the invention to provide
end-capping reagents comprised of aryl-substituted acetylene
compounds, suitable for preparing the aforementioned oligomeric
precursor compounds.
[0015] It is an additional object of the invention to provide an
integrated circuit device in which metallic circuit lines on a
substrate are electrically insulated from each other by a
dielectric material that comprises a dielectric composition of the
invention.
[0016] Still a further object of the invention is to provide an
integrated circuit packaging device (multichip module) that
incorporates a dielectric material comprising a dielectric
composition of the invention.
[0017] Additional objects, advantages and novel features of the
invention will be set forth in part in the description which
follows, and in part will become apparent to those skilled in the
art upon examination of the following, or may be learned by
practice of the invention.
[0018] In a first embodiment of the invention, then, an oligomeric
precursor compound is provided that can be imidized and crosslinked
to prepare a dielectric material, the oligomeric precursor compound
having the structural formula (I) 1
[0019] wherein:
[0020] n is an integer of 2 or more;
[0021] q is 0 or 1;
[0022] R is an oligomeric unit comprised of polyamic acid, a
polyamic acid ester, a polybenzoxazole or a polybenzothiazole;
[0023] R.sup.1 is an aromatic group optionally substituted at one
or more available carbon atoms with an inert, nonhydrogen
substituent and optionally containing one or more heteroatoms;
[0024] L is a linking group, and, as q may be 0, is optional;
and
[0025] Ar is arylene optionally substituted at one or more
available carbon atoms with an inert, nonhydrogen substituent and
optionally containing one or more heteroatoms.
[0026] In a related embodiment, the invention pertains to
end-capping reagents useful in synthesizing the aforementioned
oligomeric precursor compounds, wherein the reagents are comprised
of aryl-substituted acetylene compounds generally having the
structural formula (II) 2
[0027] wherein R.sup.1, L, q, n and Ar are as defined above, and Z
is a reactive moiety such as OH, NH.sub.2, COOH, halo, or the
like.
[0028] In another embodiment of the invention, a novel dielectric
composition is provided by heating the aforementioned oligomeric
precursor in a manner effective to bring about imidization of the
central "R" segment of the precursor and crosslinking, or "curing,"
at the bis(arylethynyl)aryl-substituted termini. Generally, this
involves heating to a predetermined temperature, at a predetermined
heating rate, and a predetermined heating time. Preferably, the
temperature for preparing the dielectric composition from the
oligomeric precursor compound is at least about 250.degree. C.,
more preferably at least about 400.degree. C. The dielectric
composition so prepared has a dielectric constant of less than
about 3.0, a thermal expansion coefficient of less than
10.sup.-3.degree. C..sup.-1, and a number of advantages chemical
and mechanical properties, e.g., enhanced mechanical and polishing
characteristics, enhanced isotropic optical and dielectrical
properties, low thermal film stress, resistance to cracking,
increased breakdown voltage, optical clarity, good adhesion to a
substrate, and the like.
[0029] In a further embodiment of the invention, an integrated
circuit device is provided that comprises: (a) a substrate; (b)
individual metallic circuit lines positioned on the substrate; and
(c) a dielectric composition positioned over and/or between the
individual metallic circuit lines, the dielectric composition
comprising an imidized, cured oligomer precursor compound, the
precursor compound having the structural formula (I), i.e.,
comprising a polyamic acid segment, polyamic acid ester segment, or
the like, capped at each terminus with a moiety
--Ar(--C.ident.C--(L).sub.q--R.sup.1).sub.n wherein Ar, L, q, n,
and R.sup.1 are as defined above.
[0030] Still an additional embodiment of the invention relates to
an integrated circuit packaging device providing signal and power
current to an integrated circuit chip, the packaging device
comprising:
[0031] (i) a substrate having electrical conductor means for
connection to a circuit board,
[0032] (ii) a plurality of alternating electrically insulating and
conducting layers positioned on the substrate wherein at least one
of the electrically insulating layers is comprised of a dielectric
composition comprising an imidized, cured oligomer precursor
compound having the structure of formula (I), i.e., comprising a
polyamic acid or polyamic acid ester segment capped at each
terminus with a moiety --Ar(--C.ident.C--(L).sub.q--R.sup.1).sub.n
wherein Ar, L, q, n, and R.sup.1 are as defined above; and
[0033] (iii) a plurality of vias for electrically interconnecting
the electrical conductor means, the conducting layers and the
integrated circuit chip.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a cross-sectional view of a portion of an
integrated circuit device of the present invention.
[0035] FIGS. 2-5 show a process for making an integrated circuit
device of the present invention.
[0036] FIGS. 6-8 show an alternative process for making an
integrated circuit device of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Overview and Definitions:
[0038] Before describing the present invention in detail, it is to
be understood that this invention is not limited to specific
compositions, components or process steps, as such may vary. It is
also to be understood that the terminology used herein is for the
purpose of describing particular embodiments only, and is not
intended to be limiting.
[0039] It must be noted that, as used in this specification and the
appended claims, the singular forms "a," "and," and "the" include
plural referents unless the context clearly dictates otherwise.
Thus, for example, reference to "an oligomeric compound" or "an
oligomeric precursor compound" includes more than one such
compound, reference to "a substituent" includes more than one
substituent, reference to "a layer" includes multiple layers, and
the like.
[0040] In describing and claiming the present invention, the
following terminology will be used in accordance with the
definitions set out below.
[0041] The term "oligomer" is used to refer to a chemical compound
that comprises linked monomers, and that may or may not be linear;
in the context of the present invention, the "oligomers" are,
however, generally linear. Oligomeric "segments" as used herein
refer to an oligomer that is covalently bound to two additional
moieties, generally end-capping moieties at each of two termini of
the oligomeric "segment." Typically, the oligomeric precursor
compounds herein have a number average molecular weight (Me) in the
range of approximately 5000 to 20,000 g/mol.
[0042] The term "alkyl" as used herein refers to a branched or
unbranched saturated hydrocarbon group of 1 to 24 carbon atoms,
such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,
t-butyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl
and the like, as well as cycloalkyl groups such as cyclopentyl,
cyclohexyl and the like. The term "lower alkyl" intends an alkyl
group of one to six carbon atoms, preferably one to four carbon
atoms.
[0043] The term "alkenyl" as used herein refers to a branched or
unbranched hydrocarbon group of 2 to 24 carbon atoms containing at
least one double bond, typically containing one to six double
bonds, more typically one or two double bonds, e.g., ethenyl,
n-propenyl, n-butenyl, octenyl, decenyl, and the like, as well as
cycloalkenyl groups such as cyclopentenyl, cyclohexenyl and the
like. The term "lower alkenyl" intends an alkenyl group of two to
six carbon atoms, preferably two to four carbon atoms.
[0044] The term "alkynyl" as used herein refers to a branched or
unbranched hydrocarbon group of 2 to 24 carbon atoms containing at
least one triple bond, e.g., ethynyl, phenylethynyl, n-propynyl,
n-butynyl, octynyl, decynyl, and the like, as well as cycloalkynyl
groups such as cyclooctynyl, cyclononynyl, and the like. The term
"lower alkynyl" intends an alkynyl group of two to six carbon
atoms, preferably two to four carbon atoms.
[0045] The term "alkylene" as used herein refers to a difunctional
branched or unbranched saturated hydrocarbon group of 1 to 24
carbon atoms, such as methylene, ethylene, n-propylene, n-butylene,
n-hexylene, decylene, tetradecylene, hexadecylene, and the like.
The term "lower alkylene" refers to an alkylene group of one to six
carbon atoms, preferably one to four carbon atoms.
[0046] The term "alkenylene" as used herein refers to a
difunctional branched or unbranched hydrocarbon group of 2 to 24
carbon atoms containing at least one double bond, such as
ethenylene, n-propenylene, n-butenylene, n-hexenylene, and the
like. The term "lower alkenylene" refers to an alkylene group of
two to six carbon atoms, preferably two to four carbon atoms.
[0047] The term "alkynylene" as used herein refers to a
difunctional branched or unbranched hydrocarbon group of 2 to 24
carbon atoms containing at least one triple bond, such as
ethynylene, n-propynylene, n-butynylene, and the like. The term
"lower alkynylene" refers to an alkynylene group of two to six
carbon atoms, preferably two to four carbon atoms, with ethynylene
particularly preferred.
[0048] The term "alkoxy" as used herein refers to a substituent
--Q--R wherein R is alkyl as defined above. The term "lower alkoxy"
refers to such a group wherein R is lower alkyl.
[0049] The term "aryl" as used herein, and unless otherwise
specified, refers to an aromatic moiety containing one to five
aromatic rings. For aryl groups containing more than one aromatic
ring, the rings may be fused or linked. Aryl groups are optionally
substituted with one or more inert, nonhydrogen substituents per
ring; suitable "inert, nonhydrogen" substituents include, for
example, halo, haloalkyl (preferably halo-substituted lower alkyl),
alkyl (preferably lower alkyl), alkenyl (preferably lower alkenyl),
alkynyl (preferably lower alkynyl), alkoxy (preferably lower
alkoxy), alkoxycarbonyl (preferably lower alkoxycarbonyl), carboxy,
nitro, cyano and sulfonyl. Unless otherwise indicated, the term
"aryl" is also intended to include heteroaromatic moieties, i.e.,
aromatic heterocycles. Generally, although not necessarily, the
heteroatoms will be nitrogen, oxygen or sulfur.
[0050] The term "arylene" as used herein, and unless otherwise
specified, refers to a bifunctional aromatic moiety containing one
to five aromatic rings. Arylene groups are optionally substituted
with one or more substituents per ring as set forth above for
substitution of an "aryl" moiety.
[0051] The term "halo" is used in its conventional sense to refer
to a chloro, bromo, fluoro or iodo substituent. In the compounds
described and claimed herein, halo substituents are generally
fluoro or chloro. The terms "haloalkyl," "haloaryl" (or
"halogenated alkyl" or "halogenated aryl") refer to an alkyl or
aryl group, respectively, in which at least one of the hydrogen
atoms in the group has been replaced with a halogen atom.
[0052] The term "heterocyclic" refers to a five- or six-membered
monocyclic structure or to an eight- to eleven-membered bicyclic
heterocycle. The "heterocyclic" substituents herein may or may not
be aromatic, i.e., they may be either heteroaryl or
heterocycloalkyl. Each heterocycle consists of carbon atoms and
from one to three, typically one or two, heteroatoms selected from
the group consisting of nitrogen, oxygen and sulfur, typically
nitrogen and/or oxygen. The term "nonheterocyclic" as used herein
refers to a compound that is not heterocyclic as just defined.
[0053] The term "hydrocarbyl" is used in its conventional sense to
refer to a hydrocarbon group containing carbon and hydrogen, and
may be aliphatic, alicyclic or aromatic, or may contain a
combination of aliphatic, alicyclic and/or aromatic moieties.
Aliphatic and alicyclic hydrocarbyl may be saturated or they may
contain one or more unsaturated bonds, typically double bonds. The
hydrocarbyl substituents herein generally contain 1 to 24 carbon
atoms, more typically 1 to 12 carbon atoms, and may be substituted
with various substituents and functional groups.
[0054] The term "inert" to refer to a substituent or compound means
that the substituent or compound will not be modified either in the
presence of the reagents or under the conditions normally employed
in the manufacture of integrated circuit devices. As explained
above, and as intended throughout, "inert, nonhydrogen
substituents" include, but are not limited to, halo, haloalkyl
(preferably halo-substituted lower alkyl), alkyl (preferably lower
alkyl), alkoxy (preferably lower alkoxy), alkoxycarbonyl
(preferably lower alkoxycarbonyl), carboxy, nitro, cyano, silyl,
trialkylsilyl, and sulfonyl.
[0055] The term "available" to refer to an optionally substituted
carbon atom refers to a carbon atom that is covalently bound to one
or more hydrogen atoms that can be replaced by a designated
substituent without disrupting or destabilizing the remaining
structure of the molecule.
[0056] "Optional" or "optionally" means that the subsequently
described circumstance may or may not occur, so that the
description includes instances where the circumstance occurs and
instances where it does not. For example, the phrase "optionally
substituted" means that a non-hydrogen substituent may or may not
be present, and, thus, the description includes structures wherein
a non-hydrogen substituent is present and structures wherein a
non-hydrogen substituent is not present.
[0057] Oligomeric Precursor Compounds:
[0058] The dielectric compositions of the invention that are
useful, inter alia, in the manufacture of integrated circuit
devices, are prepared from an oligomeric precursor compound having
the structure of formula (I) 3
[0059] wherein n, q, R, R.sup.1, L and Ar are generally defined
above.
[0060] More specifically:
[0061] Each Ar group is preferably substituted with two
--C.ident.C--(L).sub.q--R.sup.1 groups that are ortho to each other
on Ar; thus, in the preferred embodiment, n is 2. Ar is
heterocyclic or nonheterocyclic arylene optionally substituted at
one or more available carbon atoms with an inert, nonhydrogen
substituent, as noted above. Preferred Ar groups are
nonheterocyclic, including, for example, phenylene, naphthylene,
biphenylene, and phenylene, naphthylene and biphenylene optionally
substituted at one or more available carbon atoms with an inert,
nonhydrogen substituent. In a particularly preferred embodiment, Ar
is phenylene.
[0062] While the linking group L may be present, it is optional.
Thus, q is 0 or 1. Generally and preferably q is 0. When q is 1 and
L is, therefore, present, L normally represents a hydrocarbyl
linker such as alkylene, alkylene, or the like, optionally
substituted with one or more inert nonhydrogen substituents and
optionally containing nonhydrocarbyl linkages, e.g., --O--, --S--,
--NH--, or the like.
[0063] R.sup.1 is aromatic, and may be heterocyclic or
nonheterocyclic, monocyclic or polycyclic, and substituted at one
or more available carbon atoms with an inert, nonhydrogen
substituent. Examples of R.sup.1 substituents include phenyl,
naphthyl, biphenyl, anthranyl, indenyl, furanyl, pyridinyl,
pyrimidyl, thiophenyl, benzofuranyl, benzothiophenyl, indolyl,
quinolinyl, and the like.
[0064] R is an oligomeric unit comprised of polyamic acid, polyamic
acid ester, polybenzoxazole, a polybenzothiazole, or the like,
preferably polyamic acid or a polyamic acid ester, but in a
particularly preferred embodiment is a polyamic acid ester. In the
latter case, the oligomeric segment R comprises the reaction
product of (a) a diamine, and (b) a diester diacyl halide formed
from reaction of a tetracarboxylic dianhydride with a lower alkanol
and, subsequently, with a suitable halogenating agent such as an
oxalyl halide, thionyl, chloride, and the like. The diamine has the
structural formula H.sub.2N--R.sup.2--NH.sub.2 in which R.sup.2 is
a difunctional monocyclic or bicyclic aromatic moiety, typically
although not necessarily selected from the group consisting of
4
[0065] wherein X is lower alkylene, lower alkenylene, carbonyl, O,
S, SO.sub.2, NH, N(alkyl), N(aryl), dialkylsilyl, phosphonyl, if
lower alkylene or lower alkenylene, optionally substituted at one
or more available carbon atoms with halogen, halo-substituted lower
alkyl or phenyl. Specific R.sup.2 groups within the aforementioned
include, but are not limited to, the following: 5
[0066] wherein Y is selected from the group consisting of
trifluoromethyl, phenyl and phenyl substituted with one or more
inert, nonhydrogen substituents, with phenyl preferred.
Particularly preferred aromatic diamines include, but are not
limited to: p-phenylene diamine; 4,4'-diamino-diphenylamine;
benzidine; 4,4'-diamino-diphenyl ether; 1,5-diamino-naphthalene;
3,3'-dimethyl-4,4'diamino-biphenyl; 3,3'dimethoxybenzidine;
1,4-bis(p-aminophenoxy) benzene; 1,3-bis(p-aminophenoxy) benzene;
2,2-bis[4-aminophenyl]hexafluoropropane; 1,1-bis
(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane ("3FDA"); and
9,9-bis (4-aminophenyl) fluorene ("FDA").
[0067] The R.sup.2 moiety in the diamine may also be an aliphatic
or cycloaliphatic group such as cycloalkylene, e.g., cyclohexylene.
Suitable aliphatic diamines include 1,4-diaminocyclohexane and bis
(4-aminocyclohexyl) methane, 1,4-diamino-2,2,2-bicyclooctane,
1,3-diaminoadamantane,1,3-bis-p-aminophenyladamantane, etc.
[0068] The most preferred diamines for forming the polyamic acid
ester segment are 3,3'-bis-trifluoromethoxy benzidine ("TFMOB"),
4,4-oxydianiline and 3,3'-bis-trifluoromethyl benzidine
("BTFB").
[0069] The tetracarboxylic dianhydride has the structural formula
6
[0070] wherein Q is a tetrafunctional aromatic moiety, preferably
monocyclic, bicyclic or tricyclic, and is typically selected from
the group consisting of 7
[0071] Suitable dianhydrides include, without limitation:
pyromellitic dianhydride; benzophenone dianhydride;
2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;
3,3',4,4'-biphenyltetracarboxylic acid dianhydride;
bis(3,4-dicarboxyphenyl) ether dianhydride; bis(3,4dicarboxyphenyl)
thioether dianhydride; bisphenol-A bisether dianhydride;
2,2-bis(3,4-dicarboxylphenyl)hexafluoropropane dianhydride;
2,3,6,7-naphthalenetetracarboxylic acid dianhydride;
bis(3,4-dicarboxyphenyl) sulfone dianhydride; 1,2,5,6-naphthalene
tetracarboxylic dianhydride; 2,2',3,3'-biphenyl tetracarboxylic
dianhydride; 9,9-bis-(trifluoromethyl) xanthenetetracarboxylic
dianhydride; 9-trifluoromethyl-9-phenyl xanthenetetracarboxylic
dianhydride; 3,4,3',4'-benzophenone tetracarboxylic dianhydride;
and terphenyldianhydride.
[0072] The oligomeric precursor compound (I) is prepared by
synthesizing the oligomeric unit R in the presence of a
predetermined quantity of an end-capping moiety
Z--Ar(C.ident.C--(L).sub.q--R.sup.1).sub.n, wherein R.sup.1, L, q,
n and Ar are as defined above, and Z is a reactive moiety such as
OH, NH.sub.2, COOH, halo, or the like, but is preferably NH.sub.2.
Generally, this involves an amidization reaction wherein (a) a
diamine H.sub.2N--R.sup.2--NH.sub.2, as described above, is reacted
with (b) a diester diacyl halide formed from reaction of a
tetracarboxylic dianhydride, also as described above, with a lower
alkanol and halogenating reagent such as an oxalyl halide, in the
presence of (c) the end-capping moiety
Z--Ar(C.ident.C--(L).sub.q--R.sup.1).sub.n. That is, the diester
diacyl halide is formed by sequentially reacting the corresponding
tetracarboxylic dianhydride with a lower alkanol such as ethanol
and a halogenation reagent such as an oxalyl halide, e.g., oxalyl
chloride, in the presence of the end-capping moiety. The rate of
subsequent imidization can be varied by employing different
alcohols and/or different ester substituents, as the electronic
substituent effect of various ester substituents (e.g., an ethyl
ester substituent as results from reaction with ethanol) will
change the reaction rate. Alcohols useful in the aforementioned
reaction will be known to those skilled in the art and are
disclosed in the pertinent literature and texts, e.g., Advances in
Polymer Science: High Performance Polymers, ed. Hergenrother (New
York: Springer-Verlag, 1994), at page 139. Suitable diester diacyl
chlorides are diethyldichloropyromellitate, diethyl
dichlorobiphenyl tetracarboxylate and diethyldichloro
oxydiphthalate. Other suitable diamines and diester diacyl
chlorides will be known to those skilled in the art such as those
disclosed in U.S. Pat. No. 4,720,539 and copending commonly
assigned U.S. patent application Ser. No. 08/058,303 filed May 10,
1992.
[0073] In synthesizing the oligomeric compound (I), the diamine,
the diester diacyl halide and the end-capping reagent are dissolved
in a suitable solvent, preferably a polar, aprotic solvent such as
N-methylpyrrolidone, dimethylacetamide, dimethylformamide,
tetrahydrofuran, cyclohexanone, .gamma.-butyrolactone, or the like,
in proper stoichiometric amounts. Generally, the diamine and
diester diacyl halide are present in an approximately 1:1 molar
ratio, with the amount of end-capping reagent
Z--Ar(C.ident.C--(L).sub.q--R.sup.1).sub.n calculated from the
Carothers equation to provide the desired molecular weight of the
product. The oligomeric compound (I) so provided preferably has a
number average molecular weight (Mn) of about 5000 to 20,000 g/mol.
Compound (I) can be isolated and purified using conventional
techniques known to those skilled in the art.
[0074] An example of a specific compound of structural formula (I)
is as follows: 8
[0075] wherein R is 9
[0076] and, as may be seen, the polyamic ester substituent is
ethyl.
[0077] Dielectric Compositions:
[0078] The oligomeric precursor compound having the structural
formula (I) is readily converted to a dielectric material by
heating to a suitable temperature to bring about imidization of the
oligomeric segment R, chain extension, and crosslinking at the
end-capped termini. This reaction may be conducted neat or in a
solvent, preferably neat. Suitable solvents are those in which the
oligomeric compound substantially dissolves and which has a
viscosity convenient for coating, as in the manufacture of
integrated circuits, the primary application herein, polymerization
is conducted on a substrate. The solution will generally comprise
from about 5 to 80, preferably 10 to 70, weight percent solids.
Examples of suitable solvents include, for example
N-methylpyrrolidone, dimethylacetamide, dimethylformamide,
diphenylether, and the like. When polymerization is conducted in a
solvent, crosslinking and chain extension are controlled to
maintain polymer solubility (B-staging of thermosets).
[0079] The time, temperature and heating rate that are most
advantageous in the imidization, chain extension, and crosslinking
process will vary, depending on the specific oligomeric precursor
used. In general, the oligomer is heated to a temperature of at
least about 250.degree. C. to bring about imidization of the
central oligomeric segment R, chain extension, and crosslinking of
the end-capped termini, with the temperature maintained thereat for
a time period of at least about 1 hour, and preferably for 2 hours
or more. Then, crosslinking is effected at a higher temperature,
preferably at least about 400.degree. C., with the elevated
temperature maintained for a time period of at least about 1 hour,
and preferably for 2 hours or more.
[0080] This imidization and crosslinking step is preferably
conducted on a substrate. In such a case, the oligomeric precursor
compound (I) may be applied to a substrate using any number of
techniques, e.g., solution deposition, dip coating, spin coating,
spray coating, doctor blading, or the like. The substrate on which
polymerization may be conducted can be any material that has
sufficient integrity to be coated with the oligomeric precursor and
thermal stability to withstand the elevated temperatures used in
the polymerization process. Representative examples of substrates
include silicon, silicon dioxide, glass, silicon nitride, ceramics,
aluminum, copper and gallium arsenide. Other suitable substrates
will be known to those skilled in the art. In a multilayer
integrated circuit device, an underlying layer of insulated circuit
lines can also function as a substrate.
[0081] The dielectric composition so prepared, typically present as
a layer on a substrate, has a dielectric constant less than 3.0 and
more preferably less than 2.8 at 80.degree. C. The dielectric
composition has a low thermal expansion coefficient at elevated
temperatures (e.g., less than about 10.sup.-3.degree. C..sup.-1
(i.e., 1000 ppm) at 450.degree. C., preferably less than about
5.times.10.sup.-4.degree. C..sup.-1, more preferably less than
about 10.sup.-4.degree. C..sup.-1, to avoid film cracking during
subsequent thermal process steps. The dielectric composition has
enhanced mechanical and polishing characteristics, improved
isotropic optical properties, and enhanced dielectric properties.
The composition also has thermal stress of less than 100 MPa,
preferably less than 50 MPa. Further, the dielectric composition
has mechanical properties that enable it to be
chemically/mechanically planarized to facilitate lithographic
formation of multiple circuit levels in multilevel integrated
circuit devices. The dielectric composition has increased breakdown
voltage, enhanced toughness, and increased crack resistance, even
in high ambient humidity and in a thick film. The dielectric
composition is optically clear and adheres well to substrates. The
composition undergoes minimal shrinkage during heating, typically
less than about 10%.
[0082] Integrated Circuit Devices:
[0083] The primary use of the novel dielectric compositions is in
the manufacture of integrated circuit devices. An integrated
circuit device according to the present invention is exemplified in
FIG. 1, wherein the device is shown as comprising substrate 2,
metallic circuit lines 4, and a dielectric material 6 of the
present invention. The substrate 2 has vertical metallic studs 8
formed therein. The circuit lines function to distribute electrical
signals in the device and to provide power input to and signal
output from the device. Suitable integrated circuit devices
generally comprise multiple layers of circuit lines that are
interconnected by vertical metallic studs.
[0084] Suitable substrates 2 comprise silicon, silicon dioxide,
glass, silicon nitride, ceramics, aluminum, copper, and gallium
arsenide. Suitable circuit lines generally comprise a metallic,
electrically conductive material such as copper, aluminum,
tungsten, gold or silver, or alloys thereof. Optionally, the
circuit lines may be coated with a metallic liner such as a layer
of nickel, tantalum or chromium, or with other layers such as
barrier or adhesion layers (e.g., SiN, TiN, or the like).
[0085] The invention also relates to processes for manufacturing
integrated circuit devices containing a dielectric composition as
described and claimed herein. Referring to FIG. 2, the first step
of one process embodiment involves disposing on a substrate 2 a
layer 10 of an oligomeric precursor compound of the invention such
as a bis-phenylacetylene end-capped polyamic ester. The oligomeric
precursor is dissolved in a suitable solvent such as
dimethylpropylene urea ("DMPU"), N-methylpyrrolidone, or the like,
and is applied to the substrate by art-known methods such as spin-
or spray-coating or doctor blading. The solution uniquely has high
solids content (e.g. 40-50%) which leads to enhanced planarization.
The precursor compound is then thermally treated as described in
the preceding section so as to bring about imidization, chain
extension and crosslinking, thus converting layer 10 to a
dielectric composition.
[0086] Referring to FIG. 3, the third step of the process involves
lithographically patterning the layer 10 of dielectric composition
to form trenches 12 (depressions) therein. The trenches 12 shown in
FIG. 3 extend to the substrate 2 and to the metallic studs 8.
Lithographic patterning generally involves: (i) coating the layer
10 of the dielectric composition with a positive or negative
photoresist such as those marketed by Shipley or Hoechst Celanese,
(AZ photoresist); (ii) imagewise exposing (through a mask) the
photoresist to radiation such as electromagnetic, e.g., UV or deep
UV; (iii) developing the image in the resist, e.g., with suitable
basic developer; and (iv) transferring the image through the layer
10 of dielectric composition to the substrate 2 with a suitable
transfer technique such as reactive ion blanket or beam etching
(RIE). Suitable lithographic patterning techniques are well known
to those skilled in the art such as disclosed in Introduction to
Microlithography, 2nd Ed., eds. Thompson et al. (Washington, D.C.:
American Chemical Society, 1994).
[0087] Referring to FIG. 4, in the fourth step of the process for
forming an integrated circuit of the present invention, a metallic
film 14 is deposited onto the patterned dielectric layer 10.
Preferred metallic materials include copper, tungsten, and
aluminum. The metal is suitably deposited onto the patterned
dielectric layer by art-known techniques such as chemical vapor
deposition (CVD), plasma-enhanced CVD, electro and electroless
deposition (seed-catalyzed in situ reduction), sputtering, or the
like.
[0088] Referring to FIG. 5, the last step of the process involves
removal of excess metallic material by "planarizing" the metallic
film 14 so that the film is generally level with the patterned
dielectric layer 10. Planarization can be accomplished using
chemical/mechanical polishing or selective wet or dry etching.
Suitable methods for chemical/mechanical polishing are known to
those skilled in the art.
[0089] Referring to FIGS. 6-8, there is shown an alternative
process for making an integrated circuit device of the invention.
The first step of the process in this embodiment involves
depositing a metallic film 16 onto a substrate 18. Substrate 18 is
also provided with vertical metallic studs 20. Referring to FIG. 7,
in the second step of the process, the metallic film is
lithographically patterned through a mask to form trenches 22.
Referring to FIG. 8, in the third step of the process, a layer 24
of an oligomeric precursor compound of the invention is deposited
onto the patterned metallic film 16. In the last step of the
process, the oligomeric precursor compound is heated to imidize the
oligomeric central segment and crosslink the precursor's termini;
imidization and crosslinking (curing) result in a dielectric
material. Optionally, the dielectric layer may then be planarized,
if necessary, for subsequent process in a multilayer integrated
circuit.
[0090] The invention additionally relates to an integrated circuit
packaging device (multichip module) for providing signal and power
current to one or more integrated circuit chips comprising: (i) a
substrate having electrical conductor means for connection to a
circuit board; (ii) a plurality of alternating electrically
insulating and conducting layers positioned on the substrate
wherein at least of the layers comprises a film of a dielectric
material of the present invention; and (iii) a plurality of vias
for electrically interconnecting the electrical conductor means,
conducting layers and integrated circuit chips.
[0091] The integrated circuit packaging device represents an
intermediate level of packaging between the integrated circuit chip
and the circuit board. The integrated circuit chips are mounted on
the integrated circuit packaging device which is in turn mounted on
the circuit board.
[0092] The substrate of the packaging device is generally an inert
substrate such as glass, silicon or ceramic; suitable inert
substrates also include epoxy composites, polyimides, phenolic
polymers, high temperature polymers, and the like. The substrate
can optionally have integrated circuits disposed therein. The
substrate is provided with electrical conductor means such as
input/output pins (I/O pins) for electrically connecting the
packaging device to the circuit board. A plurality of electrically
insulating and electrically conducting layers (layers having
conductive circuits disposed in an dielectric insulating material)
are alternatively stacked up on the substrate. The layers are
generally formed on the substrate in a layer-by-layer process
wherein each layer is formed in a separate process step.
[0093] The packaging device also comprises receiving means for
receiving the integrated circuit chips. Suitable receiving means
include pinboards for receipt of chip I/O pins or metal pads for
solder connection to the chip. Generally, the packaging device also
comprises a plurality of electrical vias generally vertically
aligned to electrically interconnect the I/O pins, the conductive
layers and integrated circuit chips disposed in the receiving
means. The function, structure and method of manufacture of such
integrated circuit packaging devices are well known to those
skilled in the art, as disclosed, for example in U.S. Pat. Nos.
4,489,364, 4,508,981, 4,628,411 and 4,811,082.
[0094] It is to be understood that while the invention has been
described in conjunction with the preferred specific embodiments
thereof, that the foregoing description as well as the examples
which follow are intended to illustrate and not limit the scope of
the invention. Other aspects, advantages and modifications within
the scope of the invention will be apparent to those skilled in the
art to which the invention pertains.
[0095] All patents, patent applications, and publications mentioned
herein are hereby incorporated by reference in their
entireties.
[0096] Experimental:
[0097] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how to prepare and use the oligomers and polymers
disclosed and claimed herein. Efforts have been made to ensure
accuracy with respect to numbers (e.g., quantities, temperature,
etc.) but some errors and deviations should be accounted for.
Unless indicated otherwise, parts are parts by weight, temperature
is in .degree. C. and pressure is at or near atmospheric.
Additionally, all starting materials were obtained commercially or
synthesized using known procedures.
EXAMPLE 1
[0098] This example describes synthesis of
ortho-bis(phenylethynyl)phenyl end-capped poly(amic ethyl
ester).
[0099] (a) Synthesis of 3,4-Diiodophenylamine:
[0100] A 3-neck 1000 mL flask fitted with a water condenser, an
overhead stirrer and under nitrogen, was charged with
3-iodophenylamine (74.92 g, 0.34 mol). 300 mL of ethanol (EtOH) was
added and the 3-iodophenylamine dissolved with stirring. To the
solution, mercury (II) oxide (HgO) (55.57 g, 0.26 mol) was added,
the resulting bright orange solution was kept under nitrogen. With
continues stirring, iodine (12)(86.82 g, 0.34 mol) was introduced
in 10 g increments. The dark orange solution was heated to
50.degree. C. and was left stirring under nitrogen for 24
hours.
[0101] The resulting brown solution with dark brown precipitate was
dissolved in ethyl acetate (EtAc) and was filtered through celite.
The solution was concentrated and extracted with EtAc/sodium
bisulfate/brine. The organic layer was collected and dried over
anhydrous magnesium sulfate. The crude product was subjected to
flash chromatography using EtAc/hexane 1:3 as the eluent. The
solvent was evaporated on a rotary evaporator yielding black
crystals. The product recystallized from EtOH and water yielding
20.78 g white crystals (17.6%).
[0102] (b) Synthesis of 3,4-Bis(phenylethynyl)phenylamine:
[0103] In a 500 mL round bottom flask, dissolved
3,4-diiodophenylamine (15.31 g, 44.39 mmol) in 30 ml of
acetonitrille (CH.sub.3CN), followed by the addition of pyridine
(5.43 g, 68.66 mmol). To the resulting orange solution,
trifluoroacetic anhydride (15.30 g, 72.84 mmol) was slowly added
with stirring. The solution was allowed to stir for 1 hour. The
solution was poured into a 2 L beaker containing 1.5 L ice water.
The resulting suspension was vacuum filtered, washed with water and
allowed to air dry. The pink solid was then transferred into a
tarred round bottom flask and was dried under high vacuum, to
obtain 19.44 g (99%) of
N-(3,4-diiodophenyl)-2,2,2-trifluoroethanamide as a pink solid.
N-(3,4-diiodophenyl)-2,2-2-trifluoroethanamide (19.0 g, 43.09 mmol)
was transferred into a 3 neck 250 mL round bottom flask and
dissolved in phenyl acetylene (13.14 g, 14.13 mL, 128.68 mmol) with
50 ml of triethylamine (Et.sub.3N), followed by the addition of
triphenyl phosphine (2.25 g, 8.57 mmol) as a solid. The solution
was cooled to -77C., under argon. The resulting orange solution was
allowed to warm up to room temperature and while under an argon
flow, a catalytic amount of copper iodide (Cul) (0.35 g, 1.71 mmol)
and bis-triphenyl phospine palladium (II) chloride
((((C.sub.6H.sub.5).sub.3P).sub.2)Cl.sub.2) (1.20 g, 1.71 mmol)
with 50 mL Et.sub.3N was added. The solution was heated to
80.degree. C. with stirring for 12 hours. The dark brown solution
was cooled then extracted into ethyl acetate with dilute HCl and
brine. The solvent was removed and the crude product was purified
by flash chromatography using 20% EtAc in hexane as eluent. A
mixture of 4.27 g of the trifluoroacetamide-protected product, a
light brown solid, and 7.91 g of 3,4-bis(phenylethynyl)phenylamine
(88%), a viscous brown oil, were isolated. The protected product
could be quantitatively converted to the desired product by
reacting it with a aqueous potassium carbonate solution.
[0104] (3) Synthesis of Ortho-bis(phenylethynyl)phenyl end-capped
poly(amic ethyl ester), 5K oligomer:
[0105] A 50 mL three-neck flask fitted with an overhead stirrer was
charged with 0.26 g (0.88 mmol) of
3,4-bis(phenylethynyl)phenylamine, 3.44 g (1.21 mmol) of
3,3'-bis(trifluoromethoxy)benzidine (TFMOB) and 17 ml
N-methyl-2-pyrrolidinone (NMP). The flask was heated with stirring
under an argon stream in order to dissolve the diamine. After a
homogeneous solution was obtained the flask was cooled to 5.degree.
C. and a solution of 1.35 g (3.88 mmol) of
4,6-dicarbethoxyisophthalic diacylchloride (m-PMDA) in 15 mL of TUF
was added dropwise. The solution was allowed to warm to room
temperature and stir for 24 h. The resulting viscous poly(amic
ethyl ester) solution was precipitated into methanol/water (1:1)
filtered and washed with water 3.times., methanol 2.times. and
hexane. The oligomer powder was vacuum dried to constant weight,
2.5 g (.about.98%). Molecular weight (5K) was evaluated by GPC, NMR
and intrinsic viscosity measurements.
EXAMPLE 2
[0106] Film Formation:
[0107] The poly(amic ethyl ester) oligomer from Example 1 was
dissolved in NMFP. A clear solution was formed with a solids
content of 45 wt. %. The solution was subsequently cast by spin
coating onto glass plates to form films from 1 to 10 microns thick.
The imidization was accomplished by heating the polymer films for 1
hr. each at 200.degree. C., 300.degree. C. and 400.degree. C. under
an N.sub.2 atmosphere. The cured polyimide films were subsequently
cooled, slowly, to room temperature. The cured polyimide were
crack-free, exhibited a dielectric constant of about 3.0 at
80.degree. C., thermal stress of about 45 Mpa, and a thermal
expansion coefficient at 450.degree. C. of 75.times.10.sup.-6.
* * * * *