U.S. patent application number 11/414347 was filed with the patent office on 2007-11-01 for thermally stable low dielectric norbornene polymers with improved solubility and adhesion property.
Invention is credited to Kook Heon Char, Jin Kyu Lee, Joo Hyeon Park, Seung Jae Yang, Dong Woo Yoo.
Application Number | 20070255031 11/414347 |
Document ID | / |
Family ID | 38649154 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070255031 |
Kind Code |
A1 |
Lee; Jin Kyu ; et
al. |
November 1, 2007 |
THERMALLY STABLE LOW DIELECTRIC NORBORNENE POLYMERS WITH IMPROVED
SOLUBILITY AND ADHESION PROPERTY
Abstract
The present invention provides norbornene-based copolymers for
which one monomer is at least selected from a group consisting of
norbornene and dicyclopentadiene, and the other from
norbornene-based comonomers of Formula 1 shown below: ##STR1## In
Formula 1, R.sub.1, R.sub.2 and a are defined in this
specification. The present invention provides insulating elements
for multi-chip packages and antireflection films for the exposure
process of semiconductor fabrication using said norbornene-based
copolymers. Norbornene-based copolymers according to the present
invention have low dielectric constant as well as high thermal
stability and excellent solubility to various organic solvents.
Inventors: |
Lee; Jin Kyu; (Seoul,
KR) ; Yoo; Dong Woo; (Hwaseong-si, KR) ; Yang;
Seung Jae; (Jeonju-si, KR) ; Char; Kook Heon;
(Seoul, KR) ; Park; Joo Hyeon; (Metropolitan City,
KR) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1825 EYE STREET NW
Washington
DC
20006-5403
US
|
Family ID: |
38649154 |
Appl. No.: |
11/414347 |
Filed: |
May 1, 2006 |
Current U.S.
Class: |
526/283 ;
430/270.1; 430/319; 438/780; 526/280; 526/281 |
Current CPC
Class: |
C08F 232/08 20130101;
C08G 61/08 20130101 |
Class at
Publication: |
526/283 ;
526/280; 526/281; 430/270.1; 430/319; 438/780 |
International
Class: |
C08F 136/00 20060101
C08F136/00 |
Claims
1. Norbornene-based copolymers containing at least one monomer
selected from the group of norbornene and dicyclopentadiene, and
the other norbornene-based comonomer of Formula 1 shown below:
##STR9## wherein, in Formula 1, R.sub.1 and R.sub.2 are
independently selected from a group consisting of hydroxy group,
and linear or branched C.sub.1-12 alkoxy groups, substituted or not
substituted with phenyl groups; and "a" is an integral of 0 to
4.
2. Norbornene-based copolymers according to claim 1, wherein the
content of the norbornene-based comonomer of Formula 1 in
norbornene-based copolymers is greater than 0 and less than or
equal to 20 mol %.
3. Norbornene-based copolymers according to claim 1, being
copolymers of Formula 2: ##STR10## wherein, in Formula 2, R.sub.1
and R.sub.2 are independently selected from a group consisting of
hydroxy group, and linear or branched C.sub.1-12 alkoxy groups, not
substituted or substituted with phenyl groups; "a" is an integral
of 0 to 4; "m" is an integral of 100-200; "n" is an integral of
200-400; and each of the comonomers is located randomly in the
copolymer.
4. Insulating materials for multi-chip packaging, using the
norbornene-based copolymers according to claim 1.
5. Insulating materials for multi-chip packaging, using the
norbornene-based copolymers according to claim 2.
6. Insulating materials for multi-chip packaging, using the
norbornene-based copolymers according to claim 3.
7. An antireflective film for use in semiconductor fabrication,
comprising: norbornene-based copolymers containing at least one
monomer selected from the group of norbornene and
dicyclopentadiene, and the other norbornene-based comonomer of
Formula 1 shown below: ##STR11## wherein, in Formula 1, R.sub.1 and
R.sub.2 are independently selected from a group consisting of
hydroxy group, and linear or branched C.sub.1-12 alkoxy groups,
substituted or not substituted with phenyl groups; and "a" is an
integral of 0 to 4.
8. The antireflective film of claim 7, wherein the content of the
norbornene-based comonomer of Formula 1 in norbornene-based
copolymers is greater than 0 and less than or equal to 20 mol
%.
9. The antireflective film of claim 7, wherein the norbornene-based
copolymers are copolymers of Formula 2: ##STR12## wherein, in
Formula 2, R.sub.1 and R.sub.2 are independently selected from a
group consisting of hydroxy group, and linear or branched
C.sub.1-12 alkoxy groups, not substituted or substituted with
phenyl groups; "a" is an integral of 0 to 4; "m" is an integral of
100-200; "n" is an integral of 200-400; and each of the comonomers
is located randomly in the copolymer.
10. A semiconductor fabrication method comprising: using an
antireflective film during the exposure process, wherein the
antireflective film comprises norbornene-based copolymers
containing at least one monomer selected from the group of
norbornene and dicyclopentadiene, and the other norbornene-based
comonomer of Formula 1 shown below: ##STR13## wherein, in Formula
1, R.sub.1 and R.sub.2 are independently selected from a group
consisting of hydroxy group, and linear or branched C.sub.1-12
alkoxy groups, substituted or not substituted with phenyl groups;
and "a" is an integral of 0 to 4.
11. The semiconductor fabrication method of claim 10 wherein the
content of the norbornene-based comonomer of Formula 1 in
norbornene-based copolymers is greater than 0 and less than or
equal to 20 mol %.
12. The semiconductor fabrication method of claim 10 wherein the
norbornene-based copolymers are copolymers of Formula 2: ##STR14##
wherein, in Formula 2, R.sub.1 and R.sub.2 are independently
selected from a group consisting of hydroxy group, and linear or
branched C.sub.1-12 alkoxy groups, not substituted or substituted
with phenyl groups; "a" is an integral of 0 to 4; "m" is an
integral of 100-200; "n" is an integral of 200-400; and each of the
comonomers is located randomly in the copolymer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0001] FIG. 1 represents the .sup.1H-NMR spectrum of the
norbornene-based comonomer of Example 2 according to the present
invention.
[0002] FIG. 2 represents the .sup.1H-NMR spectrum of the
norbornene-based comonomer of Example 8 according to the present
invention.
[0003] FIGS. 3 to 5 are the graphs showing thermal degradation
behavior of norbornene-based copolymers depending on the content of
norbornene-based comonomers according to the present invention.
[0004] FIG. 6 is the graph representing the glass transition
temperature of the norbornene-based copolymer of Example 21
according to the present invention.
[0005] FIG. 7 represents the method of stud-pull test and the graph
of the adhesion strength of norbornene polymers.
TECHNICAL FIELD
[0006] The present invention is related to norbornene-based
copolymers. More specifically, the present invention concerns with
norbornene-based copolymers with low dielectric constant as well as
excellent solubility to various common organic solvents.
BACKGROUND ART
[0007] Due to recent rapid development of information and
communication techniques, astronomical amount of data needs to be
processed or stored at a fast rate. As a result, semiconductor
chips in one electronic system are required to transform from the
mono-chip form to the multi-chip package form connecting several
chips by a paratactically treating way. For use in circuits of such
multi-chip packages, the development of low dielectric insulating
materials with excellent thermal and mechanical properties is
essential. Particularly, in view of reducing signal delays and
capacitances being critical to the device performance, the timely
development of insulating filling materials with lower dielectric
constant is required. Moreover, low dielectric materials used as,
for example, interlayer dielectric materials of thin film
transistors of liquid crystal displays or other electronic devices
are the core elements of the devices because such low dielectric
materials can function as protecting integrated circuits,
increasing the processing rate of the devices, reducing the power
consumption, and reducing the weight of the devices. Consequently,
the development of such low dielectric materials with properties,
which can be compatible with existing and/or future fabrication
methods, is crucial.
[0008] According to the ITRS (International Technology Roadmap for
Semiconductors) prediction of U.S. semiconductor industry, low
dielectric materials for multi-chip packages, that are to be
developed before the year 2005, must have excellent properties such
as a dielectric constant of no more than 2.0, thermal stability
above 300.degree. C. and low hygroscopicity among others. In
addition, after the year 2005, there will be additional requirement
for materials to develop ultrafast data processing systems based on
optical circuits as well as on electronic circuits. Organic
thin-film materials targeted for such optoelectronic systems must
have a relevant index of refraction, high optical transparency, and
low loss of light.
[0009] Conventionally, silicon oxide films (SiO.sub.2) have been
dominantly used for the insulating materials of semiconductor
packages as well as interlayer insulating elements. However, since
SiO.sub.2 has a high dielectric constant above 4.0, it has already
reached the limitation to be considered as interchip packaging
materials of the next generation. Accordingly, various trials have
already been conducted to develop low dielectric materials for the
next-generation packages. Examples of low dielectric materials
developed up until now include polyimides, benzocyclobutenes,
polynorbornenes, and so forth.
[0010] Polyimides among the group mentioned above have a high
dielectric constant of 2.9.about.3.5 and high hygroscopicity, and
electrical/optical anisotropy occurs in polyimides due to its
inherent chemical structures. Benzocyclobutenes developed by Dow
also have a high dielectric constant of about 2.7. Moreover, the
process to prepare thin films based on benzocyclobutenes is known
to be rather complex and their adhesion to metal surfaces are
poor.
[0011] Polynorbornenes have excellent properties such as high
thermal stability, low hygroscopicity, electrical/optical isotropy
among others but have poor adhesion to metals. Recently, BF
Goodrich synthesized a new class of polynorbornenes by
incorporating a silicon compound containing alkoxy groups to the
norbornene monomer in order to improve the adhesion to metals.
However, the prepared polynorbornene has a high dielectric constant
of about 2.7. Thus, materials with excellent thermal and mechanical
properties, yet maintaining low dielectric constant, are required
for use as an element for semiconductor packages of the next
generation.
[0012] From the fabrication perspectives, on the other hand, above
mentioned low-dielectric materials should also possess excellent
solubility to common organic solvents. Conventional
norbornene-based copolymers, however, have poor solubility to
organic solvents. As a result, when optoelectronic systems are to
be fabricated by spin-coating using such conventional
norbornene-based copolymers, there are drawbacks such that a
certain solvent must be used at a higher temperature. In order to
resolve this kind of drawback, various trials have been conducted
such as controlling the design of comonomers used in the
copolymers, the content of comonomer in the copolymers, molecular
weight of the copolymers, and so forth.
DISCLOSURE OF THE INVENTION
[0013] Present inventors have found that when norbornene-based
monomers based on hydroxybenzene and/or alkoxybenzene are used as
one comonomer component in norbornene-based copolymers, solubility
of such norbornene-based copolymers in organic solvents is greatly
improved. In particular, present inventors have found that when a
norbornene-based monomer comprising alkoxybenzene is used as a
comonomer, thermal stability of norbornene-based copolymer also can
be improved.
[0014] Thus, the present invention provides norbornene-based
copolymers with improved solubility to organic solvents and also
with high enough thermal stability commensurate with current
fabrication process.
[0015] The present invention provides norbornene-based copolymers
incorporating at least one monomer selected from the group
consisting of norbornene and dicyclopentadiene, and the other from
norbornene-based comonomers of Formula 1, shown below. ##STR2##
[0016] In Formula 1, R.sub.1 and R.sub.2 are independently selected
from a group consisting of hydroxy group, and linear or branched
C.sub.1-12 alkoxy group not substituted or substituted with phenyl
group. The letter "a" is an integral of 0 to 4.
[0017] Moreover, the present invention provides insulating elements
for multi-chip packages and antireflection films for the exposure
process of semiconductor fabrication, using the norbornene-based
copolymers of the present invention.
[0018] The present invention is described in detail below.
[0019] As described above, norbornene-based copolymers have
excellent properties such as heat resistance, low hygroscopicity,
electrical-optical isotropy, high optical transparency, and so
forth Consequently, the test on their applicability to multi-chip
packages of the next generation and to optical circuit materials in
optoelectronic systems is increasingly of interest. However, the
norbornene-based materials in their conventional form have poor
solubility to most of organic solvents and thus inevitably pose
several problems in fabrication processes. These present inventors
have found that when norbornene-based monomers comprising
hydroxybenzene and/or alkoxybenzene are used as one comonomer
component during the preparation of norbornene-based copolymers,
the solubility to organic solvents of such norbornene-based
copolymers are greatly improved. A detailed explanation is provided
below.
[0020] In general, solubility of one polymer to many common organic
solvents can be improved by introducing alkyl groups in chain form
to the chemical structure of a comonomer because the alkyl groups
introduced as such provide flexibility to polymer backbones and
sterically hinder the intermolecular interaction among polymer
chains. However, although the introduction of such alkyl groups to
the polymer could increase the solubility to organic solvents, it
is also known that it, at the same time, reduces the glass
transition temperature (Tg) of the prepared polymer.
Norbornene-based copolymers also have similar tendency to such
ordinary polymers. In preparing norbornene-based copolymers, when a
norbornene-based monomer decorated with alkyl groups in its
chemical structure is used as one of comonomers for copolymers, the
alkyl group substituted norbornene comonomer imparts the
flexibility to the otherwise stiff structure of norbornene-based
copolymers so as to improve the solubility of such norbornene-based
copolymers to organic solvents. However, the alkyl group
substituted norbornene comonomer not only imparts the structural
flexibility to norbornene-based copolymers, but also decreases the
glass transition temperatures (Tg) of the norbornene-based
copolymers reducing thermal stability, which is one of the merits
of the norbornene-based copolymers.
[0021] However, the present invention uses the norbornene-based
monomers containing alkoxybenzene or hydroxybenzene as one
comonomer component in preparing norbornene-based copolymers. By
this rational design of new norbornene-based monomers, the present
invention renders the norbornene-based copolymers with improved
their solubility in many common organic solvents but still
maintaining the thermal stability of the norbornene-based
copolymers. More specifically, the comonomers used in the present
invention not only have alkyl group(s) in alkoxy moieties but also
incorporate benzene rings with planar structure. Thus, the alkyl
groups in the alkoxy part of the comonomer impart flexibility to
the chemical structure of the norbornene-based copolymers and
sterically hinder intermolecular interactions so as to improve the
solubility to many common organic solvents. At the same time,
benzene rings with stiff planar chemical structure keep the glass
transition temperature of the norbornene-based copolymers at high
temperature so as to maintain the thermal stability of the
norbornene-based copolymers. This is to say that the
norbornene-based copolymers prepared according to the present
invention have greatly improved solubility to most common organic
solvents and, at the same time, thermal property at the level
similar to norbornene homopolymer.
[0022] In the present invention not only the solubility to various
organic solvents but also the thermal property of norbornene-based
copolymers can be controlled. The preparation of thin films for
optoelectronic systems, typically by solvent casting of the
copolymers described herein prepared with one comonomer containing
various kinds of alkoxybenzenes or hydroxybenzene, is thus greatly
facilitated.
[0023] In the present invention, the content of the comonomer in
the norbornene-based copolymers is preferably greater than 0 and
less than or equal to 20 mol %. When the content of the comonomer
in the norbornene-based copolymers exceed 20 mol %, the comonomer
may affect properties such as mechanical and thermal properties of
the prepared norbornene copolymers. In addition, the comonomers
described above are expected to be quite expensive. Thus, due to
the high cost of such comonomers, it is not preferable that a
copolymer contains such a comonomer in excess of the above content
range. Even though the content of the comonomer is no more than 5
mol % in the norbornene-based copolymers of the present invention,
the comonomer can provide the above effects of the present
invention.
[0024] The comonomer of Formula 1 can be easily prepared by the
simple liquid phase reaction, not by high temperature and high
pressure processes that are generally employed for preparing
norbornene-based derivatives. For example, the comonomer of Formula
1 can be prepared by stirring starting materials such as
benzoquinone-based material and cyclopentadiene in organic solvents
at room temperature, and then allowing them to react together for a
few hours. The starting materials to obtain the comonomer(s) of
Formula 1 can be easily purchased, for example, from chemical
distribution agents like Aldrich, but not limited to it only.
Methods to synthesize the comonomer(s) of Formula 1 are illustrated
in the following examples, and those skilled in the art can modify
the methods to prepare various kinds of the comonomers according to
the present invention.
[0025] Norbornene-based copolymers prepared according to the
present invention include a copolymer consisting of norbornene and
the comonomer of Formula 1, a copolymer consisting of
dicyclopentadiene and the comonomer of Formula 1, and a copolymer
consisting of norbornene, dicyclopentadiene, and the comonomer of
Formula 1.
[0026] Dicyclopentadiene has a chemical structure wherein one
pentagonal ring is bonded to the norbornene as shown in the formula
below. Thus, the backbone structure of the copolymers containing
norbornene and the comonomer of Formula 1 is nearly similar to that
of a copolymer consisting of dicyclopentadiene and the comonomer of
Formula 1, or to that of a copolymer consisting of norbornene,
dicyclopentadiene and the comonomer of Formula 1. Accordingly,
their fundamental properties such as thermal property and
solubility to organic solvent are also similar. ##STR3##
[0027] Norbornene-based copolymers according to the present
invention have the structure of Formula 2, shown below.
##STR4##
[0028] In Formula 2, R.sub.1 and R.sub.2 are independently selected
from a group consisting of hydroxy group, and linear or branched
C.sub.1-12 alkoxy group, substituted or not substituted with phenyl
group(s), the letter "a" is an integral of 0 to 4, "n" is an
integral of 100 to 200, and "n" is an integral of 200 to 400,
whereby each of the comonomers is located randomly in the
copolymer.
[0029] Norbornene-based copolymers according to the present
invention can be prepared by reacting norbornene and/or
dicyclopentadiene and the comonomer of Formula 1 in a relevant
solvent at room temperature. Detailed methods to prepare the
norbornene-based copolymers according to the present invention are
illustrated in the examples below.
[0030] Norbornene-based copolymers according to the present
invention have excellent solubility to most of common organic
solvents such as methylenechloride, tetrahydrofuran, benzene,
toluene, chlorobenzene, chloroform, and so forth due to the
norbornene-based comonomer(s) containing hydroxybenzene and/or
alkoxybenzene in the copolymer.
[0031] Norbornene-based copolymers according to the present
invention have enhanced adhesion property onto the substrates such
as silicone wafer and metal surface. In addition, the
norbornene-based copolymers according to the present invention have
a glass transition temperature in the range of 300.degree.
C..about.400.degree. C., depending on the composition of the
copolymers.
[0032] The present invention also provides an insulating material
for a semiconductor package and an antireflective film for an
exposure process of a semiconductor fabrication, prepared by using
the norbornene-based copolymer of the present invention.
[0033] For example, a thin film can be easily prepared by the spin
coating of the copolymer(s) prepared according to the present
invention. This means that while the copolymer solution in a
predetermined concentration is filtered by a filter (for example,
0.2 .mu.m filter), the copolymer solution is immediately dropped on
a silicon wafer of which the surface can also be pretreated in
advance. Then, a thin-film with a desirable thickness is prepared
by changing the rotational number (rpm) of a spin coater. A final
thin film is formed by heat-treating the thin-film prepared as
described above under air at 90.about.220.degree. C. to evaporate
remaining residual solvent. The heat treatment must be performed at
a temperature that is no larger than the glass transition
temperature of the copolymer. If the heat treatment is performed at
a temperature above the glass transition temperature of the
copolymer, the chains of the norbornene-based copolymer have enough
activation to move the center-of-mass of each chain, enabling a
roughened film surface. Films prepared described above can be used
as an insulating element for multi-chip packages and also as an
antireflective film in the exposure process of semiconductor
fabrication.
EXAMPLES
[0034] The present invention is further illustrated or detailed in
the following examples. However, the examples provided here are
only for illustrating the present invention, and the present
invention is not just defined by the examples provided here.
[0035] Preparation of Norbornene-Based Comonomer(s)
Example 1
Synthesis of a norbornene comonomer I
(1,4-dihydro-1,4-methanonaphthalene-5,8-diol)
[0036] 16 g of benzoquinone was added to the solution made by 10 g
of cyclopentadiene dissolved in 100 mL of methylenechloride (MC)
while the solution is refluxed at 150.degree. C. Then, the mixture
was cooled to 0.degree. C. and stirred for 3 hours. A reduction
reaction of the product produced by the reaction was conducted by
additions of 50 mL of ethyl acetate and 20 g of aluminum oxide and
by ultrasonic exposure for 1 hour. A yellowish solid was obtained
and the product yield was 80% (20 g). ##STR5##
Example 2
Synthesis of a norbornene-based comonomer II
(5,8-diethoxy-1,4-dihydro-1, 4-methanonaphthalene)
[0037] 10 g of 1,4-dihydro-1,4-methanonaphthalene-5,8-diol
synthesized in Example 1 was added to 20 mL of dimethyl sulfoxide,
followed by an addition of 12.9 g of KOH and the mixture was
stirred for 30 minutes. 12.5 g of ethyl bromide was further added
and then the mixture was reacted for 30 minutes. After the
reaction, 50 mL of water and 50 mL of methylenechloride were poured
into the reaction mixture for extraction. After the organic phase
was separated from the aqueous phase, 5 g of Na.sub.2SO.sub.4 was
added to the organic phase. Then, the organic phase was filtered
off Na.sub.2SO.sub.4 and distilled off the solvent. As a result, a
yellowish solid was obtained and the product yield was 99% (13.1
g). ##STR6##
Example 3
Synthesis of a norbornene-based comonomer III
(5,8-dibenzyloxy-1,4-dihydro-1,4-methanonaphthalene)
[0038] 5,8-dibenzyloxy-1,4-dihydro-1,4-methanonaphthalene was
prepared by performing the same process as Example 2, except that
19.6 g of benzyl bromide was used instead of 12.5 g of ethyl
bromide. Yield: 96% ##STR7##
Example 4
Syntheses of a norbornene-based comonomer IV
(5,8-dioctyloxy-1,4-dihydro-1,4-methanonaphthalene)
[0039] 5,8-dioctyloxy-1,4-dihydro-1,4-methanonaphthalene was
prepared by performing the same process as Example 2, except that
22 g of octyl bromide was used instead of 12.5 g of ethyl bromide.
Yield: 93% ##STR8##
[0040] Synthesis of Norbornene-Based Copolymer
Example 5 to Example 10
[0041] In a reactor containing 100 mL of methylenechloride (MC),
allyl palladium chloride dimer as a catalyst and silver
hexafluoroantimonate as an anion were added and then sufficiently
stirred for 30 minutes by a stirrer. Then, 9 g of norbornene and 1
g of a norbornene-based comonomer described in Table 1 below were
added to the reactor and the mixture was reacted at room
temperature for 12 hours. Then, the mixture was dropped to a
methanol/hydrochloric acid (9/1) solution (200 mL), and thus, a
solid precipitation was yielded. After the precipitation was
filtered and a little solvent remaining in the precipitation was
removed, a white polymer was obtained. TABLE-US-00001 TABLE 1
[Norbornene]/ [Comonomer] [Catalyst]/ Example Comonomer (g/g)
[Monomer] Yield 5 Example 1 9/1 1/500 45% 6 Example 2 9/1 1/125 75%
7 Example 2 9/1 1/250 69% 8 Example 2 9/1 1/500 78% 9 Example 3 9/1
1/500 72% 10 Example 4 9/1 1/500 75%
Example 11 to Example 24
[0042] [Pd(CH.sub.3CH.sub.2CN).sub.4][SbF.sub.6].sub.2 was added as
a catalyst to a reactor containing 100 mL of methylenechloride and
the mixture was stirred for 30 minutes. Then, norbornene and the
norbornene-based comonomer prepared in Examples 1 to 4 were added
in an amount described in Table 2 below and the mixture was reacted
at room temperature for 12 hours. The mixture was dropped to a
methanol/hydrochloric acid (9/1) solution (200 mL) to form a
precipitation. After the precipitation was filtered and a small
amount of solvent remaining in the precipitation was removed under
vacuum, a white polymer was obtained. TABLE-US-00002 TABLE 2
[Norbornene]/ [Comonomer] [Catalyst]/ Example Comonomer (g/g)
[Monomer] Yield 11 Example 2 9/1 1/125 82% 12 Example 2 9/1 1/250
80% 13 Example 2 9/1 1/500 78% 14 Example 2 9/1 1/1000 77% 15
Example 2 9.5/0.5 1/125 70% 16 Example 2 9.5/0.5 1/500 72% 17
Example 2 8/2 1/125 56% 18 Example 2 8/2 1/500 63% 19 Example 3
0/10 1/50 7% 20 Example 3 9/1 1/125 76% 21 Example 3 9/1 1/500 72%
22 Example 4 0/10 1/50 4% 23 Example 4 9/1 1/125 56% 24 Example 4
9/1 1/500 45%
[0043] Solubility of Norbornene-based Copolymer in organic
solvent
Comparative Experiment 1, Experiments 2 to 5
[0044] Solubility in organic solvents was determined for a
conventional norbornene homopolymer (PNB) and norbornene-based
copolymers of the present invention prepared in Examples 5, 13, 21
and 24. The results are shown in Table 3 below. Solubility was
determined by dissolving 0.5 g of each polymer in 1 mL of each
solvent. When the polymer dissolves in the solvent, it is shown as
O. When the polymer does not dissolve in the solvent, it is shown
as X. TABLE-US-00003 TABLE 3 Solvent Comparable (Relative
Experiment 1 Experiment 2 Experiment 3 Experiment 4 Experiment 5
Polarity) (PNB) (Example 5) (Example 13) (Example 21) (Example 24)
Toluene X .largecircle. .largecircle. .largecircle. .largecircle.
(2.3) Chloroform X .largecircle. .largecircle. .largecircle.
.largecircle. (4.8) THF(7.6) X .largecircle. .largecircle.
.largecircle. .largecircle. Methylene X .largecircle. .largecircle.
.largecircle. .largecircle. chloride (MC) (8.9) Chlorobenzene
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle.
[0045] In Table 3, the numbers in parenthesis next to the name of
the solvent indicate relative polarity. The higher the number, the
higher the polarity.
[0046] As described in Table 3, norbornene homopolymer (PNB)
dissolved in only chlorobenzene, but copolymers according to the
present invention dissolved in chloroform, THF and
methylenechloride that have relatively high polarity. In addition,
while PNB displayed low solubility of 0.1 g/mL in chlorobenzene,
copolymers prepared in Examples 5, 13, 21 and 24 displayed
solubility above 1 g/mL.
[0047] Thermal Stability of Norbornene-Based Copolymers
[0048] Thermal analysis results for the norbornene-based copolymer
of the present invention prepared in Examples 6 to 8 are shown in
FIG. 3. Thermal analysis results for the copolymer in Examples 11
to 13 are shown in FIG. 4. Thermal analysis results for the
copolymer in Examples 20, 21, 23 and 24 are shown in FIG. 5.
Through these figures, it is found that the thermal stability of
the copolymers prepared in the examples according to the present
invention is similar to that of a conventional norbornene
homopolymer.
[0049] In addition, FIG. 6 shows a glass transition temperature
determined for norbornene homopolymer (PNB) and the copolymer
prepared in Example 21 (Dynamic Mechanical Analysis). As shown in
FIG. 6, the glass transition temperature of the copolymer prepared
in Example 21 is lower than that of PNB by about 20.degree. C.
Because the glass transition temperature of norbornene copolymer
comprising alkyl groups is generally lower than that of PNB by
100.degree. C., the glass transition temperature of the copolymer
in Example 21 is not significantly different from that of PNB.
[0050] Adhesion Property
[0051] The adhesion force of the copolymers onto a substrate
(typically, silicon wafer) is qualitatively tested by the tape test
and the stud-pull test, as documented in the ASTM D335997 and ASTM
D517902, respectively. Although the tape test does not yield any
quantitative adhesion values, it is regarded as a simple and easy
method to check preliminary adhesion against a substrate of
interest to screen many possible candidate materials. For the tape
test, the norbornene-based copolymers were spin-coated on silicon
wafers. Scotch tape was then applied firmly to a fixed area of the
film and removed quickly from the surface of the film. The
copolymer film, after removal of a scotch tape, was checked under a
microscope to check any delamination that could occur as a result
of the adhesive failure at the interface between the copolymer film
and the substrate. In the case where no delamination was observed
under the microscope, the copolymer films were immersed in boiling
water for one hour. If the copolymer film is not peeled off from
the substrate during the test, the copolymer film is classified as
a film with good adhesion. From this tape test (reliability was
confirmed with repeated experiments more than 3 times with freshly
prepared), we are able to compare the relative adhesion property
among PNB and the copolymer in Examples 13, 21, and 24, as
summarized in Table 4. TABLE-US-00004 TABLE 4 Entry Film Thickness
(.mu.m) Tape Test PNB 0.8 .+-. 0.05.sup.a Fail Example 13 1.2 .+-.
0.07 Pass Example 21 0.6 .+-. 0.05 Pass Example 24 0.9 .+-. 0.05
Pass
[0052] More quantitative data for the adhesion of the copolymers
were obtained from the stud-pull test by ASTM D 517902. The
adhesion between polymer and metal was tested by pulling the stubs
apart in an Instron at a crosshead speed of 50 mm/min. The adhesion
strength was calculated by dividing the force necessary to separate
the stubs by the area of the upper stub. The adhesion of norbornene
copolymers to aluminum and copper was tested by detection of
failure at the interface between the polymer and metal. In FIG. 7,
the copolymers have stronger adhesion strength than norbornene
homopolymer because of the oxygen functional group in the
comonomer. And the copolymer in Examples 21 and 24 has less
strength than the copolymer in Example 13. This indicates that the
bulky groups may decrease the number of the functional group
interacting with the metal as a substrate. As the bulky groups
increase the free volume of the polymer, it is conceivable that
there are less functional groups actually present at the interface
to participate in reactions with metal.
[0053] Test for Analysis of Electrical-Optical Property of Thin
Film Formed by Using Norbornene-Based Copolymer
[0054] The solution was prepared by dissolving 20 wt % of the
copolymer prepared according to the present invention in
mesitylene. Then, thin film of the solution was prepared by spin
coating at 2000 rpm for 30 seconds. The thickness of the thin film
was determined at about 2 .mu.m by a Prism Coupler. Then, the thin
film was subjected to a heat treatment at 250 to 450.degree. C. to
prepare a copolymer thin film.
[0055] To determine the electrical property of the thin film,
aluminum electrode was deposited on the thin film under vacuum.
More particularly, the aluminum electrode was obtained in uniform
thickness of about 100 nm by depositing aluminum under the
condition of 5 mm of diameter, no more than 10.sup.-5 torr of
pressure, and no more than 0.5 nm/sec of evaporating rate.
[0056] Electrical properties of copolymers were determined by
calculating a dielectric constant from a maximum capacitance value
of a C-V (Capacitance-Voltage) curve in MIS
(Metal-Insulator-Semiconductor) structure. The dielectric constants
of the copolymers are shown in Table 4 below. TABLE-US-00005 TABLE
4 Thickness Dielectric Index of Refraction Copolymer of Thin Film
(.mu.m) Constant, k (@ 632 nm) Example 8 1.5 2.42 1.508 Example 9
1.43 2.45 1.492 Example 10 0.9 2.55 1.500 Example 11 1.38 2.12 1.27
Example 13 1.39 2.48 1.483 Example 15 1.42 2.28 1.32 Example 18
1.41 2.12 1.27 Example 21 1.01 2.48 1.492 Example 24 0.96 2.48
1.492
[0057] As described in Table 3, while the dielectric constant of
the conventional norbornene homopolymer was 2.6, the dielectric
constants of the norbornene-based copolymers prepared in the
examples were lower than 2.6
INDUSTRIAL APPLICABILITY
[0058] Norbornene-based copolymer of the present invention is
prepared by using a norbornene-based monomer having hydroxybenzene
and/or alkoxybenzene as a comonomer, so as to have an excellent
solubility to an organic solvent, thermal stability of similar
level to a conventional norbornene homopolymer, and low dielectric
constant. Thus, the norbornene-based copolymers of the present
invention are useful as an insulating material for a multi-chip
package of the next-generation and an antireflective film used in
the exposure process of semiconductor fabrication.
* * * * *