U.S. patent application number 11/392727 was filed with the patent office on 2006-08-03 for crosslinkable fluorinated aromatic prepolymer and its uses.
This patent application is currently assigned to ASAHI GLASS COMPANY, LIMITED. Invention is credited to Masahiro Ito, Kaori Tsuruoka, Shunsuke Yokotsuka.
Application Number | 20060173129 11/392727 |
Document ID | / |
Family ID | 34386193 |
Filed Date | 2006-08-03 |
United States Patent
Application |
20060173129 |
Kind Code |
A1 |
Yokotsuka; Shunsuke ; et
al. |
August 3, 2006 |
Crosslinkable fluorinated aromatic prepolymer and its uses
Abstract
To provide a crosslinkable fluorinated aromatic prepolymer which
is capable of forming a cured product having a low relative
permittivity, high heat resistance, low birefringence and high
flexibility, and its uses. A crosslinkable fluorinated aromatic
prepolymer which is obtained by subjecting a compound (Y-1) having
a crosslinkable functional group (A) and a phenolic hydroxyl group
and/or a compound (Y-2) having a crosslinkable functional group (A)
and a fluorinated aromatic ring, to a condensation reaction in the
presence of a HF-removing agent, with a fluorinated aromatic
compound (B) represented by the formula (1): ##STR1## (wherein n is
an integer of from 0 to 2, each of a and b which are independent of
each other, is an integer of 0 to 3, and each of Rf.sup.1 and
Rf.sup.2 represents a fluorinated alkyl group having at most 8
carbon atoms and a compound (C) having at least 3 phenolic hydroxyl
groups, and which has crosslinkable functional groups (A) and ether
bonds and has a number average molecular weight of from
1.times.10.sup.3 to 5.times.10.sup.5.
Inventors: |
Yokotsuka; Shunsuke;
(Yokohama-shi, JP) ; Ito; Masahiro; (Yokohama-shi,
JP) ; Tsuruoka; Kaori; (Yokohama-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ASAHI GLASS COMPANY,
LIMITED
Tokyo
JP
|
Family ID: |
34386193 |
Appl. No.: |
11/392727 |
Filed: |
March 30, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP04/14200 |
Sep 29, 2004 |
|
|
|
11392727 |
Mar 30, 2006 |
|
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Current U.S.
Class: |
524/611 ;
257/E21.264; 528/205 |
Current CPC
Class: |
H01L 21/0212 20130101;
H01L 21/3127 20130101; H01L 21/02282 20130101; C08G 65/4025
20130101 |
Class at
Publication: |
524/611 ;
528/205 |
International
Class: |
C08L 69/00 20060101
C08L069/00; C08G 63/78 20060101 C08G063/78 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2003 |
JP |
2003-340031 |
Claims
1. A crosslinkable fluorinated aromatic prepolymer which is
obtained by subjecting either one or both of a compound (Y-1)
having a crosslinkable functional group (A) and a phenolic hydroxyl
group and a compound (Y-2) having a crosslinkable functional group
(A) and a fluorinated aromatic ring, to a condensation reaction in
the presence of a HF-removing agent, with a fluorinated aromatic
compound (B) represented by the following formula (1): ##STR6##
(wherein n is an integer of from 0 to 2, each of a and b which are
independent of each other, is an integer of from 0 to 3, and each
of Rf.sup.1 and Rf.sup.2 which may be the same or different from
each other, represents a fluorinated alkyl group having at most 8
carbon atoms, and F in the aromatic ring represents that hydrogen
atoms of the aromatic ring are all substituted by fluorine atoms),
and a compound (C) having at least 3 phenolic hydroxyl groups, and
which has crosslinkable functional groups (A) and ether bonds and
has a number average molecular weight of from 1.times.10.sup.3 to
5.times.10.sup.5.
2. The crosslinkable fluorinated aromatic prepolymer according to
claim 1, wherein the crosslinkable functional group (A) is an
ethynyl group.
3. A cured product formed by curing the crosslinkable fluorinated
aromatic prepolymer as defined in claim 1.
4. A coating composition comprising the crosslinkable fluorinated
aromatic prepolymer as defined in claim 1, and a solvent.
5. A cured film formed by forming a wet film of a crosslinkable
fluorinated aromatic prepolymer on a substrate, by using the
coating composition as defined in claim 4, and then, after removing
the solvent in the wet film or at the same time as removing the
solvent, curing the crosslinkable fluorinated aromatic
prepolymer.
6. The cured film according to claim 5, which contains pores in the
film.
7. An electric or electronic component having the cured film as
defined in claim 5.
Description
TECHNICAL FIELD
[0001] The present invention relates to a crosslinkable aromatic
prepolymer and its uses. A cured film formed by curing the
crosslinkable fluorinated aromatic prepolymer of the present
invention has a low relative permittivity, high heat resistance,
low birefringence and high flexibility and thus is useful as an
optical transmission device or an insulation film for electric or
electronic components.
BACKGROUND ART
[0002] An insulation film having a lower relative permittivity is
required, as electronic devices, multilayer wiring boards, etc. are
increasingly small-sized and highly integrated, and as displays of
e.g. TFT are large-sized and become high-resolution. Further, as an
optical material to be used for an optical transmission device such
as an optical integrated circuit, an optical switching device or an
optical-electrical consolidated substrate, a material having high
light transmittance and low birefringence (dependency on
polarization of refractive index), is required. Fluorinated
aromatic polymers are now being studied to satisfy such
requirements and to secure heat resistance of at least 250.degree.
C., preferably at least 300.degree. C., further preferably at least
350.degree. C., which is required in the process for producing
and/or mounting electronic devices, multilayer wiring boards or
optical transmission devices.
[0003] As a fluorinated aromatic polymer, a fluorinated aromatic
polymer having ether bonds (hereinafter referred to as a
polyarylene ether or PAE) has been proposed (e.g. Patent Documents
1 to 3 and Non-Patent Document 1). Its relative permittivity is
from about 2.5 to 2.9, and its application to an insulation film
for electronic devices or multilayer wiring boards, is being
studied. Further, its application to optical transmission devices
is also being studied.
[0004] Further, PAE having a branched structure has been proposed
which is produced by using a compound having at least three
phenolic hydroxyl groups (e.g. Patent Document 4).
[0005] Further, PAE satisfying both a dielectric constant and high
Tg has been proposed which is produced from a specific fluorinated
aromatic compound having a branched structure (e.g. Patent Document
5).
[0006] Patent Document 1: Japanese Patent No. 3064011
[0007] Patent Document 2: U.S. Pat. No. 5,115,082
[0008] Patent Document 3: U.S. Pat. No. 5,959,157
[0009] Patent Document 4: JP-A-10-247646
[0010] Patent Document 5: WO03/008483
[0011] Non-Patent Document 1: J. Polm. Sci.; Part A; Polm. Chem.,
vol. 36, 2881 (1998)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0012] However, the above-described prior art has had the following
problems.
[0013] PAE disclosed in Patent Documents 1 to 3 and Non-Patent
Document 1, is a linear-chain polymer produced by using a compound
having two phenolic hydroxyl groups, and its glass transition
temperature (hereinafter referred to as Tg) is low and the heat
resistance is inadequate. Tg can be increased by introducing
crosslinkable functional groups to PAE, followed by crosslinking,
but the relative permittivity will thereby be increased to a level
of from 2.7 to 3.0. Thus, it is difficult to satisfy both a low
relative permittivity and high Tg. Further, the birefringence of
such a polymer is about 0.007, which is low as compared with a
polyimide or the like but is still inadequate as an optical
transmission device.
[0014] Further, PAE having a branched structure as disclosed in
Patent Document 4 has no crosslinkable functional group and thus is
thermoplastic, whereby Tg can hardly be made to be at least
300.degree. C.
[0015] Further, PAE produced from a specific fluorinated aromatic
compound having a branched structure as disclosed in Patent
Document 5 has a very bulky molecular structure and thus has a
drawback that it is brittle and inferior in flexibility.
Specifically, it has a drawback that particularly when a thick film
is to be formed, cracking is likely to result in the coating film
by a thermal stress.
[0016] The present invention has been made under the
above-described circumstances, and it is an object of the present
invention to provide a crosslinkable fluorinated aromatic
prepolymer which is capable of forming a cured product having a low
specific permittivity, high heat resistance, low birefringence and
high flexibility simultaneously, a coating composition containing
it, a cured product formed by using such a prepolymer, and a cured
film formed from the coating composition.
Means to Solve the Problems
[0017] In order to accomplish the above object, the present
invention provides a crosslinkable fluorinated aromatic prepolymer
which is obtained by subjecting either one or both of a compound
(Y-1) having a crosslinkable functional group (A) and a phenolic
hydroxyl group and a compound (Y-2) having a crosslinkable
functional group (A) and a fluorinated aromatic ring, to a
condensation reaction in the presence of a HF-removing agent, with
a fluorinated aromatic compound (B) represented by the following
formula (1): ##STR2## (wherein n is an integer of from 0 to 2, each
of a and b which are independent of each other, is an integer of
from 0 to 3, and each of Rf.sup.1 and Rf.sup.2 which may be the
same or different from each other, represents a fluorinated alkyl
group having at most 8 carbon atoms, and F in the aromatic ring
represents that hydrogen atoms of the aromatic ring are all
substituted by fluorine atoms), and a compound (C) having at least
3 phenolic hydroxyl groups, and which has crosslinkable functional
groups (A) and ether bonds and has a number average molecular
weight of from 1.times.10.sup.3 to 5.times.10.sup.5.
[0018] In the crosslinkable fluorinated aromatic prepolymer of the
present invention, it is preferred that the crosslinkable
functional group (A) is an ethynyl group.
[0019] Further, the present invention provides a cured product
formed by curing the above crosslinkable fluorinated aromatic
prepolymer.
[0020] Further, the present invention provides a coating
composition comprising the above crosslinkable fluorinated aromatic
prepolymer and a solvent.
[0021] Further, the present invention provides a cured film formed
by forming a wet film of a crosslinkable fluorinated aromatic
prepolymer on a substrate by using the above coating composition,
and then, after removing the solvent in the wet film or at the same
time as removing the solvent, curing the crosslinkable fluorinated
aromatic prepolymer.
[0022] This cured film may contain pores in the film.
[0023] Further, the present invention provides an electric or
electronic component having the above cured film.
Effects of the Invention
[0024] The crosslinkable fluorinated aromatic prepolymer of the
present invention is produced by using the compound (C) having at
least three phenolic hydroxyl groups and has crosslinkable
functional groups (A), whereby it is possible to form a cured film
which satisfies a low dielectric constant, low birefringence and
high heat resistance simultaneously.
[0025] Further, the crosslinkable fluorinated aromatic prepolymer
of the present invention is capable of forming a cured film
excellent in flexibility, whereby it is possible to obtain a film
strong against an external force such as bending, and it becomes
easy to form a thick film.
[0026] Further, the cured product formed by curing the
crosslinkable fluorinated aromatic prepolymer of the present
invention is excellent in applicability to insulation films for
electronic devices and multilayer wiring boards, films and optical
transmission devices. In such applications, it is possible to
accomplish high performance in e.g. reduction of signal
transmission delay time for an element and to gain high reliability
by excellent mechanical properties in a high temperature
region.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] The crosslinkable fluorinated aromatic prepolymer of the
present invention (hereinafter referred to simply as the
prepolymer) is characterized in that it is obtained by subjecting
either one or both of a compound (Y-1) having a crosslinkable
functional group (A) and a phenolic hydroxyl group and a compound
(Y-2) having a crosslinkable functional group (A) and a fluorinated
aromatic ring, to a condensation reaction in the presence is of a
HF-removing agent, with a fluorinated aromatic compound (B)
represented by the following formula (1): ##STR3## (wherein n is an
integer of from 0 to 2, each of a and b which are independent of
each other, is an integer of from 0 to 3, and each of Rf.sup.1 and
Rf.sup.2 which may be the same or different from each other,
represents a fluorinated alkyl group having at most 8 carbon atoms,
and F in the aromatic ring represents that hydrogen atoms of the
aromatic ring are all substituted by fluorine atoms), and a
compound (C) having at least 3 phenolic hydroxyl groups, and it has
crosslinkable functional groups (A) and ether bonds and has a
number average molecular weight of from 1.times.10.sup.3 to
5.times.10.sup.5.
[0028] The prepolymer of the present invention is produced by using
the compound (C) having at least three phenolic hydroxyl groups and
has crosslinkable functional groups (A), whereby it is possible to
obtain a cured product (a fluorinated aromatic polymer) satisfying
a low dielectric constant, low birefringence and high heat
resistance simultaneously. Namely, by using the compound (C) having
at least three phenolic hydroxyl groups, it is possible to
introduce branched structures to the polymer chain to make the
molecular structure three dimensional thereby to increase the free
volume of the polymer, whereby low densification i.e. a low
dielectric constant can be accomplished. Further, usually, a linear
chain polymer having aromatic rings is likely to undergo
orientation of molecules due to stacking of aromatic rings, and the
birefringence tends to increase. Whereas, with the cured product of
the present invention, orientation of molecules is suppressed by
the introduction of branched structures, and consequently, the
birefringence will be small.
[0029] By the presence of the crosslinkable functional groups (A),
in the obtainable cured product, a crosslinking or chain-extending
reaction among prepolymer molecules can be promoted, and
consequently, the heat resistance will be substantially be
improved. At the same time, there is an effect such that the
solvent resistance of the cured product will be improved.
[0030] Further, by the use of the fluorinated aromatic compound (B)
represented by the above formula 1, it is possible to obtain a
cured product having excellent flexibility. As compared with a
fluorinated aromatic polymer produced from a fluorinated aromatic
compound having a branched structure in itself, it is possible to
increase the density of ether bonds, whereby flexibility of the
main chain will be improved, and consequently, it is possible to
obtain a cured product having excellent flexibility. The
flexibility being excellent is advantageous particularly when the
cured product is in the form of a cured film.
[0031] In the present invention, the fluorinated aromatic compound
(B) is a fluorinated aromatic compound represented by the above
formula (1). In this formula (1), each of Rf.sup.1 and Rf.sup.2 is
a fluorinated alkyl group having at most 8 carbon atoms. From the
viewpoint of the heat resistance, a perfluoroalkyl group is
preferred. As a specific example, a perfluoromethyl group, a
perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl
group, a perfluorohexyl group or a perfluorooctyl group may be
mentioned.
[0032] If the number of Rf.sup.1 or Rf.sup.2 exceeds 2, it tends to
be difficult to produce the fluorinated aromatic compound (B).
Accordingly, the number (a or b) of Rf.sup.1 or Rf.sup.2 is
independently preferably from 0 to 2, most preferably 0. The
fluorinated aromatic compound (B) is preferably perfluorobenzene,
perfluorotoluene, perfluoroxylene, perfluorobiphenyl or
perfluoroterphenyl, particularly preferably perfluorobenzene or
perfluorobiphenyl. These compounds may be used alone or in
combination as a mixture of two or more of them. As the fluorinated
aromatic compound (B), perfluorobiphenyl is most preferred, since
the cured product thereby obtainable will be excellent in the
balance of the dielectric constant and the heat resistance, and the
flexibility of the cured product will be high.
[0033] In the present invention, the compound (C) having at least
three, preferably from 3 to 5, phenolic hydroxyl groups is
preferably a polyfunctional phenol. As a specific example,
trihydroxybenzene, trihydroxybiphenyl, trihydroxynaphthalene,
1,1,1-tris(4-hydroxyphenyl)ethane, tris(4-hydroxyphenyl)benzene,
tetrahydroxybenzene, tetrahydroxybiphenyl, tetrahydroxybinaphthyl
or a tetrahydroxyspiroindan may, for example, be mentioned. As the
compound (C), a compound having three phenolic hydroxyl groups, is
preferred, since the flexibility of a cured film thereby obtainable
will be high, and especially, trihydroxybenzene is most preferred,
since the dielectric constant of a cured product thereby obtainable
will be low.
[0034] The prepolymer of the present invention contains
crosslinkable functional groups (A). Such crosslinkable functional
groups (A) are reactive functional groups which do not
substantially undergo a reaction during the production of the
prepolymer and which undergo a reaction when an external energy is
given at the time of preparing a cured product such as a coating, a
film or a molded product or at an optional point of time after the
preparation, to induce crosslinking or chain extension among
prepolymer molecules.
[0035] As the external energy, heat, light, electron beams, etc. or
a combination thereof is preferred in view of the excellent
applicability to the production of electronic devices, multilayer
wiring boards or optical transmission devices and/or to the
mounting process. In a case where heat is employed as the external
energy, reactive functional groups which react at a temperature of
from 40.degree. C. to 500.degree. C. are preferred. If the reactive
temperature is too low, the stability cannot be secured during the
storage of the prepolymer or a coating composition containing the
prepolymer, and if it is too high, the prepolymer itself tends to
undergo heat decomposition during the reaction. Accordingly, the
temperature for the reaction is preferably within the above range,
more preferably from 60.degree. C. to 400.degree. C., most
preferably from 70.degree. C. to 350.degree. C. In a case where
light is employed as the external energy, it is also preferred to
incorporate a photo radical initiator, a photo acid generator, a
sensitizer, etc. to the prepolymer or to the after-mentioned
coating composition containing the prepolymer. Further,
crosslinkable functional groups (A) containing no polar groups will
not increase the relative permittivity of a cured film, and it is
preferred to employ crosslinkable functional groups (A) containing
no polar groups, especially when the prepolymer of the present
invention is employed for the production of an insulation film.
[0036] Specific examples of the crosslinkable functional groups (A)
include, for example, vinyl groups, allyl groups, methacryloyl(oxy)
groups acryloyl(oxy) groups, vinyloxy groups, trifluorovinyl
groups, trifluorovinyloxy groups, ethynyl groups,
1-oxocyclopenta-2,5-diene-3-yl groups, cyano groups, akoxysilyl
groups, diarylhydroxymethyl groups and hydroxyfluorenyl groups.
Vinyl groups, methacryloyl(oxy) groups, acryloyl(oxy) groups,
trifluorovinyloxy groups or ethynyl groups are preferably employed,
since the reactivity is high, and a high crosslinking density can
be obtained. Ethynyl groups are most preferred since a cured
product thereby obtainable will have excellent heat resistance.
[0037] The content of the crosslinkable functional groups (A) in
the prepolymer of the present invention is such that the
crosslinkable functional groups (A) are preferably from 0.1 to 4
mmol, more preferably from 0.2 to 3 mmol, per gram of the
prepolymer. If the content exceeds this range, brittleness of a
cured product tends to increase, and the relative permittivity may
sometimes increase. On the other hand, if it is smaller than this
range, the heat resistance and the solvent resistance of the cured
product may sometimes decrease.
[0038] The prepolymer of the present invention may be produced by
either one or both of the following methods (i) and (ii).
[0039] (i) A method wherein the fluorinated aromatic compound (B)
represented by the above formula 1, the compound (C) having at
least three phenolic hydroxyl groups and the compound (Y-1) having
a phenolic hydroxyl group are subjected to a condensation reaction
in the presence of a HF-removing agent.
[0040] (ii) A method wherein the fluorinated aromatic compound (B),
the compound (C) having at least three phenolic hydroxyl groups and
the compound (Y-2) having a crosslinkable functional group (A) and
a fluorinated aromatic ring are subjected to a condensation
reaction in the presence of a HF-removing agent.
[0041] Further, in a case where the prepolymer is produced by both
of the above (i) and (ii), the fluorinated aromatic compound (B),
the compound (C), the compound (Y-1) and the compound (Y-2) are
subjected to a condensation reaction in the presence of a
HF-removing agent.
[0042] In the above methods for producing the prepolymer, the
condensation reaction is considered to proceed as follows. As shown
in the following formula (2), an ether bond will be formed by e.g.
a reaction mechanism wherein a phenoxy group derived from a
phenolic hydroxyl group will attack the carbon atom to which a
fluorine atom of the fluorinated aromatic compound (B) is bonded,
and then the fluorine atom will be detached. Further, in a case
where the compound (C) and/or (Y-1) has two phenolic hydroxyl
groups present at an ortho position to each other, a dioxin
skeleton may be formed as shown by the following formula (3) by
e.g. a similar reaction mechanism. ##STR4##
[0043] As the compound (Y-1) having a crosslinkable functional
group (A) and a phenolic hydroxyl group to be used in the process
(i), a compound (Y-1-1) having one phenolic hydroxyl group and a
compound (Y-1-2) having two phenolic hydroxyl groups, are
preferred.
[0044] Specific examples of the compound (Y-1-1) having a
crosslinkable functional group (A) and one phenolic hydroxyl group
include a phenol having a reactive double bond such as
4-hydroxystyrene and an ethynyl phenol such as 3-ethynyl phenol,
4-phenylethynyl phenol or 4-(4-fluorophenyl)ethynyl phenol. They
may be used alone or in combination as a mixture of two or more of
them. More preferred is an aromatic compound having an ethynyl
group as the crosslinkable functional group (A).
[0045] Specific examples of the compound (Y-1-2) having a
crosslinkable functional group (A) and two phenolic hydroxyl groups
include a bis(phenylethynyl)dihydroxybiphenyl such as
2,2'-bis(phenylethynyl)-5,5'-dihydoxybiphenyl or
2,2'-bis(phenylethynyl)-4,4'-dihydroxybiphenyl, and a
dihydroxydiphenylacetylene such as 4,4'-dihydroxytolan or
3,3'-dihydroxytolan. They may be used alone or in combination as a
mixture of two or more of them.
[0046] As the compound (Y-2) having a crosslinkable functional
group (A) and a fluorinated aromatic ring to be used in the method
(ii), a compound having a crosslinkable functional group (A) and a
perfluoro aromatic ring such as perfluorophenyl or
perfluorobiphenyl, is preferred. Its specific examples include a
fluorinated aryl having a reactive double bond, such as
pentafluorostyrene, pentafluorobenzyl acrylate, pentafluorobenzyl
methacrylate, pentafluorophenyl acrylate, pentafluorophenyl
methacrylate, perfluorostyrene, pentafluorophenyltrifluorovinyl
ether or 3-(pentafluorophenyl)pentafluoropropene-1, a fluorinated
aryl having a cyano group, such as pentafluorobenzonitrile, a
fluorinated aryl acetylene such as pentafluorophenyl acetylene or
nonafluorobiphenyl acetylene, and a fluorinated diaryl acetylene
such as phenylethynyl pentafluorobenzene, phenylethynyl
nonafluorobiphenyl or decafluorotolan. They may be used alone or in
combination as a mixture of two or more of them. As the compound
(Y-2), a fluorinated arylacetylene is preferred, since the
crosslinking reaction will thereby proceed at a relatively low
temperature, and the heat resistance of a prepolymer cured product
thereby obtained will be high.
[0047] As the HF-removing agent to be used for the production of
the prepolymer of the present invention, a basic compound is
preferred, and an alkali metal carbonate, hydrogen carbonate or
hydroxide is particularly preferred. Specific examples include
sodium carbonate, potassium carbonate, sodium hydrogen carbonate,
potassium hydrogen carbonate, sodium hydroxide or potassium
hydroxide.
[0048] With respect to the amount of the HF-removing agent to be
used, in the method (i), it is required in an amount of at least
equimolar, preferably from 1.1 to 3 times in a molar ratio to the
total molar amount of phenolic hydroxyl groups in the compound (C)
and the compound (Y-1). In the method (ii), it is required in an
amount of at least equimolar, preferably from 1.1 to 3 times in a
molar ratio to the molar amount of phenolic hydroxyl groups in the
compound (C).
[0049] In the methods (i) and (ii), the condensation reaction is
preferably carried out in a polar solvent. The polar solvent is
preferably a solvent containing an aprotic polar solvent such as
N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone,
dimethyl sulfoxide or sulfolane. To the polar solvent, toluene,
xylene, benzene, tetrahydrofuran, benzotrifluoride,
xylenehexafluoride or the like may be incorporated within a range
not to deteriorate the solubility of the prepolymer to be formed or
not to adversely affect the condensation reaction. By such
incorporation, the polarity (the dielectric constant) of the
solvent may be changed to control the reaction rate.
[0050] The condensation reaction conditions are preferably from 10
to 200.degree. C. for from 1 to 80 hours, more preferably from 20
to 180.degree. C. for from 2 to 60 hours, most preferably from 50
to 160.degree. C. for from 3 to 24 hours.
[0051] The number average molecular weight of the prepolymer of the
present invention is within a range of from 1.times.10.sup.3 to
5.times.10.sup.5, preferably from 1.5.times.10.sup.3 to
1.times.10.sup.5. When it is within a range of from
1.times.10.sup.3 to 5.times.10.sup.5, the coating properties of the
after-mentioned coating composition containing such a prepolymer
will be good, and the resulting cured film will have good heat
resistance, mechanical properties, solvent resistance, etc. In an
application to an insulation film for electronic devices, when a
property to sufficiently penetrate into fine spaces of a substrate
and to make the surface smooth (so-called gap-filling and
planarization property) is required, the number average molecular
weight of the prepolymer is most preferably within a range of from
1.5.times.10.sup.3 to 5.times.10.sup.4.
[0052] The number average molecular weight of the prepolymer can be
controlled by changing the charging ratio of the fluorinated
aromatic compound (B) to the sum of the compound (C) and the
compound (Y-1) in the method (i). Here, it is preferred that no
hydroxyl groups will remain in the prepolymer, since the relative
permittivity will thereby be low. In the condensation reaction in
the present invention, the fluorinated aromatic compound (B)
usually functions as a bifunctional compound. Accordingly, control
of the molecular weight is preferably adjusted within a range where
the total molar amount of hydroxyl groups in the compound (C) and
the compound (Y-1) will not exceed twice of the molar amount of the
fluorinated aromatic compound (B).
[0053] Likewise, in the method (ii), the number average molecular
weight of the prepolymer can be controlled by changing the charging
ratio of the compound (C) to the sum of the fluorinated aromatic
compound (B) and the compound (Y-2). Also here, in the same manner
as mentioned above, control of the molecular weight is preferably
adjusted within a range wherein the total molar amount of hydroxyl
groups will not exceed the sum of the molar amount of the compound
(Y-2) and twice the molar amount of the fluorinated aromatic
compound (B), when the compound (Y-2) serves as a monofunctional
compound. Further, when the compound (Y-2) serves as a bifunctional
compound, it is preferably adjusted within a range wherein the
total molar amount of hydroxyl groups will not exceed twice the
total molar amount of the fluorinated aromatic compound (B) and the
compound (Y-2).
[0054] Further, in the method (ii), in a case where the reaction
rates of the fluorinated aromatic compound (B) and the compound
(Y-2) are different, the molecular weight for composition of the
prepolymer thereby obtainable may sometimes be different depending
upon the order of addition. For example, in a case where the
reaction rates to phenoxy groups derived from the phenolic hydroxyl
group of the compound (C) are (B)>(Y-2), if the fluorinated
aromatic compound (B) and the compound (Y-2) are charged
simultaneously, all phenoxy groups may be consumed by the
fluorinated aromatic compound (B) before all the compound (Y-2) is
consumed, whereby a non-reacted compound (Y-2) may remain. In such
a case, in order to increase the reaction rate of the compound
(Y-2), it is preferred that after charging the compound (Y-2)
first, the fluorinated aromatic compound (B) is charged. However,
in such a method, variation in the composition of the resulting
prepolymer chains tends to be large. When it is required to
minimize such variation in the composition of the resulting
prepolymer chains, it is preferred to carry out the production by
charging all at once.
[0055] In the method (i), the amount of the compound (C) to be used
is preferably from 0.1 to 1 time, more preferably from 0.3 to 0.6
time, in a molar ratio to the fluorinated aromatic compound (B),
and the amount of the compound (Y-1) to be used is preferably from
0.1 to 2 times, more preferably from 0.2 to 1.5 times, in a molar
ratio to the fluorinated aromatic compound (B). In the method (ii),
the amount of the compound (C) to be used is preferably from 0.5 to
2 times, more preferably from 0.6 to 1.5 times, in a molar ratio to
the fluorinated aromatic compound (B), and the amount of the
compound (Y-2) is preferably from 0.1 to 2 times, more preferably
from 0.2 to 1.5 times, in a molar ratio to the fluorinated aromatic
compound (B). When the respective values are in such ranges, the
resulting prepolymer will have a low dielectric constant and high
heat resistance, such being desirable.
[0056] The prepolymer of the present invention may be produced by
suitably selecting the method (i) or (ii) to obtain a prepolymer
capable of obtaining a cured product having desired physical
properties, depending upon the physical properties such as the heat
resistance, relative permittivity, birefringence, and flexibility,
of the cured product obtainable after the curing. For example, in a
case where the method (ii) is used, the relative permittivity and
birefringence values of a cured product obtainable by curing the
prepolymer thus produced usually tend to be low. Accordingly, to
obtain a cured product having low relative permittivity and
birefringence values, it is preferred to produce the prepolymer by
the method (ii).
[0057] In the present invention, in a case where the heat
resistance of a cured product of the prepolymer is inadequate or
the coating or film made of the cured product is brittle, a
co-condensation component may be incorporated at the time of the
production of the prepolymer to improve the heat resistance or
flexibility of the cured product.
[0058] Such a co-condensation component may, for example, be a
compound (Z) having two phenolic hydroxyl groups other than (Y-1)
in order to improve the flexibility of the cured film, or a
fluorinated aromatic compound (X) having a branched structure in
order to improve the heat resistance of the cured film.
[0059] The compound (Z) having two phenolic hydroxyl groups may be
a bifunctional phenol such as dihydroxybenzene, dihydroxybiphenyl,
dihydroxyterphenyl, dihydroxyonaphthalene, dihydroxyanthracene,
dihydroxyphenanthracene, dihydroxy-9,9-diphenylfluororene,
dihydroxydibenzofuran, dihydroxydiphenyl ether, dihydroxydiphenyl
thioether, dihydroxybenzophenone, dihydroxy-2,2-diphenylpropane,
dihydroxy-2,2-diphenylhexafluoropropane or dihydroxybinaphthyl.
They may be used alone or in combination as a mixture of two or
more of them.
[0060] The fluorinated aromatic compound (X) having a branched
structure may be perfluoro(1,3,5-triphenylbenzene) (the following
formula (4A)) or perfluoro(1,2,4-triphenylbenzene) (the following
formula (4B)). ##STR5##
[0061] After the condensation reaction or after formed into a
solution, the prepolymer of the present invention is purified by a
method such as neutralization, reprecipitation, extraction or
filtration. The purification is preferably carried out in a state
where the polar solvent preferably used during the production, is
present, or in a state as dissolved or dispersed in the
after-mentioned solvent, since the efficiency is thereby good. In
an application as an insulation film for electronic devices or an
insulation film for multilayer wiring boards, a metal such as
potassium or sodium as a condensation reaction catalyst and free
halogen atoms are likely to cause operation failure of a transistor
or corrosion of wiring, and accordingly, it is preferred to
sufficiently carry out the purification.
[0062] For the prepolymer of the present invention, various
catalysts or additives may be employed for the purpose of e.g.
increasing the reaction rate or reducing reaction defects during
the crosslinking reaction for curing.
[0063] In a case where the prepolymer of the present invention
contains ethynyl groups as the crosslinkable functional groups (A),
the catalyst may, for example, be an amine such as aniline,
triethylamine, aminophenyltrialkoxysilane or
aminopropyltrialkoxysilane, or an organic metal compound containing
molybdenum, nickel or the like.
[0064] As an additive to be added to the prepolymer, a
biscyclopentadienone derivative is preferred. An ethynyl group and
a cyclopentadienone group (a 1-oxocyclopenta-2,5-dien-3-yl group)
undergoes a Diels-Alder reaction by heat to form an adduct,
followed by a de-carbon monoxide reaction to form an aromatic ring.
Accordingly, if a biscyclopentadienone derivative is used,
crosslinking or chain extension can be carried out wherein an
aromatic ring constitutes a linkage moiety.
[0065] Specific examples of the biscyclopentadienone derivative
include
1,4-bis(1-oxo-2,4,5-triphenyl-cyclopenta-2,5-dien-3-yl)benzene,
4,4'-bis(1-oxo-2,4,5-triphenyl-cyclopenta-2,5-dien-3-yl)biphenyl,
4,4'-bis(1-oxo-2,4,5-triphenyl-cyclopenta-2,5-dien-3-yl)1,1'-oxybisbenzen-
e,
4,4'-bis(1-oxo-2,4,5-triphenyl-cyclopenta-2,5-dien-3-yl)1,1'-thiobisben-
zene,
1,4-bis(1-oxo-2,5-di-[4-fluorophenyl]4-phenyl-cyclopenta-2,5-dien-3--
yl)benzene,
4,4'-bis(1-oxo-2,4,5-triphenyl-cyclopenta-2,5-dien-3-yl)1,1'-(1,2-ethaned-
iyl)bisbenzene and
4,4'-bis(1-oxo-2,4,5-triphenyl-cyclopenta-2,5-dien-3-yl)1,1'-(1,3-propane-
diyl)bisbenzene.
[0066] Among these biscyclopentadienone derivatives,
biscyclopentadienone derivatives having entirely aromatic skeletons
are preferred from the viewpoint of the heat resistance. They may
be used alone or in combination as a mixture of two or more of
them.
[0067] From the prepolymer of the present invention, a cured
product can be obtained by having its cross-linking reaction
proceeded to cure it. The present invention provides a cured
product by curing such a prepolymer. The cured product may have any
shape. It is preferably a cured coating (a cured film) formed from
a coating composition containing the after-mentioned solvent. In
the following description, the present invention will be described
in detail with reference to a cured film as a preferred form.
[0068] The prepolymer of the present invention can be used suitably
as a material for a coating composition to be used for coating on a
suitable substrate and forming a film by having its condensation
reaction proceeded to cure it. Thus, the present invention provides
a coating composition comprising the above prepolymer and a
solvent.
[0069] The coating composition of the present invention can be
obtained, for example, by dissolving or dispersing the
above-mentioned prepolymer of the present invention in a
solvent.
[0070] The solvent to be used for the coating composition of the
present invention is not particularly limited so long as the
prepolymer of the present invention and a catalyst or additives
which may be added as the case requires, can be dissolved or
dispersed therein, and a cured film having a desired thickness,
uniformity or gap-filling and planarization property, can be
obtained. For example, an aromatic hydrocarbon, a dipolar aprotic
solvent, a ketone, an ester, an ether or a halogenated hydrocarbon
may be mentioned. The solvent for the coating composition may be
the same or different from the solvent for the reaction for the
production of the above-described prepolymer. If a different
solvent is to be used, the prepolymer may once be recovered from
the reaction solution by e.g. a reprecipitation method and then
dissolved or dispersed in a different solvent, or solvent
substitution may be carried out by using a known method such as an
evaporation method or an ultrafiltration method.
[0071] The aromatic hydrocarbon may, for example, be benzene,
toluene, xylene, ethylbenzene, cumene, mesitylene, tetralin or
methylnaphthalene.
[0072] The dipolar aprotic solvent may, for example, be
N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide,
y-butylolactone or dimethylsulfoxide.
[0073] The ketone may, for example, be cyclopentanone,
cyclohexanone, cycloheptanone, cyclooctanone or ethyl amyl
ketone.
[0074] The ether may, for example, be tetrahydrofuran, pyran,
dioxane, dimethoxyethane, diethoxyethane, diphenyl ether, anisole,
phenetole, diglyme or triglyme.
[0075] The ester may, for example, be ethyl lactate, methyl
benzoate, ethyl benzoate, butyl benzoate, benzyl benzoate, methyl
cellsolve acetate, ethyl cellsolve acetate, propylene glycol
monomethyl ether, propylene glycol monoethyl ether, propylene
glycol monopropyl ether, propylene glycol monobutyl ether or
propylene glycol monoethyl ether acetate.
[0076] The halogenated hydrocarbon may, for example, be carbon
tetrachloride, chloroform, methylene chloride, tetrachloroethylene,
chlorobenzene or dichlorobenzene.
[0077] With respect to the coating composition of the present
invention, the concentration of the prepolymer in the composition
is preferably from 1 to 50 mass %, more preferably from 5 to 30
mass %. This coating composition may contain, in addition to the
prepolymer and the solvent, at least one type of additives selected
from various additives well known in the coating field such as
plasticizers and thickeners. Further, to form a film or coating
having pores, the after-mentioned hollow bodies or a material which
can be removed after forming a thin film may, for example, be
suitably incorporated.
[0078] In a case where the prepolymer of the present invention
contains a low molecular weight substance having a vapor pressure,
to prevent its evaporation during the heating, a part of the
crosslinkable functional groups (A) may preliminarily be reacted in
a solution. As such a method, heating is preferred. The heating
conditions are preferably from 50.degree. C. to 250.degree. C. for
from 1 to 50 hours, more preferably from 70 to 200.degree. C. for
from 1 to 20 hours. The reaction ratio in the solution of the
crosslinkable functional groups is preferably less than 50%, more
preferably less than 30%, with a view to preventing gellation of
the prepolymer in the solution.
[0079] The coating composition of the present invention is applied
on a suitable substrate surface to form a wet film, and then, after
or at the same time as removing the solvent by e.g. evaporation,
curing treatment is applied to let the crosslinkable functional
groups (A) in the prepolymer undergo a crosslinking reaction to
form a cured film which is applicable as an insulation film and an
optical transmission device. As such a method for forming the wet
film, it is preferred to employ a coating method. For example, a
known coating method such as a spin coating method, a dip coating
method, a spray coating method, a die-coating method, a bar coating
method, a doctor coating method, an extrusion coating method, a
scan coating method, a brush coating method or a potting method may
be mentioned. In a case where it is used as an insulation film for
electronic devices, a spin coating method or a scanning coating
method is preferred from the viewpoint of uniformity of the film
thickness.
[0080] After applying this coating composition, heating is carried
out to evaporate the solvent and to cure the prepolymer by a
crosslinking or chain extension reaction. The crosslinkable
functional groups (A) of this prepolymer do not substantially react
in a solution and will undergo a crosslinking reaction in the
heating step after the film formation. The heating conditions are
preferably from 200 to 450.degree. C. for from about 1 to 120
minutes, more preferably from 250 to 400.degree. C. for from about
2 to 60 minutes.
[0081] The heating equipment is preferably a hot plate, an oven or
a furnace. The heating atmosphere may, for example, be an
atmosphere of an inert gas such as nitrogen or argon, air, oxygen
or reduced pressure. The heating atmosphere is preferably an inert
gas atmosphere or a reduced pressure atmosphere. In order to secure
the surface smoothness of the thin film or to improve fine space
gap-filling properties of the thin film, it is preferred to add a
preliminary heating step at a temperature of from about 50 to
250.degree. C. or to carry out the heating step as divided into a
plurality of stages. The reaction ratio of the crosslinkable
functional groups (A) in the cured film is preferably from 30 to
100%. When the reaction ratio is at least 30%, the heat resistance
and chemical resistance of the cured film will be good. From such a
viewpoint, the reaction ratio is more preferably at least 50%, most
preferably at least 70%.
[0082] The thickness of the wet film to be formed by the coating
composition can be optionally set to match the shape of the desired
cured film to be produced. For example, for the purpose of
producing an insulation layer or film, it is preferred to form a
wet film having a thickness of from about 0.01 to 500 .mu.m on a
substrate, and a thickness of from 0.1 to 300 .mu.m is more
preferred.
[0083] The cured film obtainable from the coating composition of
the present invention may be peeled from the substrate and used as
a film itself, or may be used as an insulation film or the like in
a state as bonded on the substrate. In the latter case, in order to
improve the adhesion between the cured film and the substrate, the
adhesion promoter may be used. As such an adhesion promoter, a
silane coupling agent, a titanate coupling agent or an aluminum
coupling agent may be mentioned, and particularly preferred is a
silane coupling agent such as an epoxysilane or an aminosilane. The
aminosilane may, for example, be an aliphatic aminosilane such as
3-aminopropylmethyldiethoxysilane or 3-aminopropyltriethoxysilane,
or an aromatic group-containing aminosilane such as
aminophenyltrimethoxysilane, aminophenyltriethoxysilane or
N-phenyl-3-aminopropyltrimethoxysilane.
[0084] As a method for applying the adhesion promoter, it is
preferred to employ a method of treating the substrate with the
adhesion promoter prior to coating with the coating composition, or
a method of adding the adhesion promoter to the coating
composition. As the method of treating the substrate with the
adhesion promoter, in the case of an aminosilane, a method of
spin-coating the substrate in the form of a 0.01 to 3 mass %
solution in an alcohol. As such an alcohol, methanol, ethanol or
isopropyl alcohol is preferred. In the method of adding the
adhesion promoter in the prepolymer solution, the amount of the
adhesive promoter to be added is preferably from 0.05 to 10 mass %,
more preferably from 0.1 to 5 mass %, based on the contained
prepolymer. If the amount of the adhesion promoter to be added is
small, the effect for improving the adhesion tends to be
inadequate, and if it is too large, the electrical properties or
heat resistance tends to decrease.
[0085] The cured product produced by using the prepolymer of the
present invention may be used for e.g. protective films, film
materials for various cells such as fuel cells, photoresists,
optical waveguides, non-linear optical materials, optical
adhesives, covering materials, electronic components, encapsulation
materials, over coating agents, transparent film materials, heat
resistance/low moisture absorbing film materials, adhesives, fiber
materials, weather resistant coating materials, water repellents,
oil repellents, moisture proof coating agents, or non-sticky
coating agents. Particularly preferred is an application to
insulation films for electronic devices or multilayer wiring
boards, films or optical transmission devices. The present
invention provides an electric or electronic component having the
cured film formed by using the coating composition comprising the
above prepolymer and a solvent.
[0086] Among electric or electronic components which the cured film
of the present invention is applicable, as electronic devices, a
discreet semiconductor such as a diode, a transistor, a compound
semiconductor, a thermistor, a varistor or a thyristor, a memory
device such as DRAM (dynamic random access memory), SRAM (static
random access memory), EPROM (erasable programmable read only
memory), mask ROM (mask read only memory), EEPROM (electrical
erasable programmable read only memory) or a flash memory, a logic
device such as a microprocessor, DSP or ASIC, an integrated circuit
device such as a compound semiconductor represented by MMIC
(monolithic microwave integrated circuit), a hybrid integrated
circuit (hybrid IC), a photoelectric conversion device such as a
light emitting diode or a charge-coupled device, and a display
device such as an amorphous silicon TFT (thin film transistor) or a
polysilicon TFT, may, for example, be mentioned.
[0087] Among the electric or electronic components to which the
insulation film of the present invention is applicable, the
multilayer wiring boards may be various substrates to mount
electronic devices, etc. thereon and may, for example, be high
density wiring boards such as a printed circuit board, a buildup
wiring board, a MCM substrate and an interposer.
[0088] As an insulation film in such electric or electronic
components, a buffer coating film, a passivation film, an
interlayer insulation film, an insulation film for redistribution
or an alpha ray shielding film may, for example, be mentioned.
[0089] The optical transmission device is meant for a component
which has a function to let light pass therethrough for
transmission, branching, amplification or optical
branching/multiplexing. The optical transmission device may, for
example, be an optical fiber, a rod lens, an optical waveguide, an
optical branching device, an optical multiplexer, an optical
branching filter, an optical attenuator, an optical switch, an
optical isolator, an optical transmitter module, an optical
receiver module, a coupler, a deflector, a light wavelength
conversion device, a light modulation device, an optical integrated
circuit, a photoelectric hybrid circuit or a substrate itself or an
optical transmission portion thereof.
[0090] The wavelength of light to be used for the optical
transmission device is preferably within a range of from 600 to
1,600 nm. Within such a range, 650 nm band, 850 nm band, 1,300 nm
band or 1,550 nm band is preferred, since a component for e.g. a
laser is thereby readily available.
[0091] In a case where the above optical transmission device is
used as a so-called electro-optic (EO) material to modulate and
control optical transmission by an external electric field to carry
out phase change, directional coupling, mode conversion or change
of the course of guided light, it is preferred to have a non-linear
optical dye doped. As such a non-linear optical dye, a compound
having a long n-conjugated system and having a push-pull type
electron structure having an electron donating group and an
electron attracting group, is preferred. As a specific example, an
azobenzene dye or a polyene dye may, for example, be mentioned.
[0092] In an application to an insulation film for electronic
devices or an insulation film for multilayer wiring boards
employing the cured film formed from the prepolymer of the present
invention, in order to obtain an insulation film having a lower
relative permittivity, it is preferred to provide pores in the
insulation film of the present invention. As a method for
introducing such pores, the following method (a) or (b) may, for
example, be mentioned.
[0093] (a) A method wherein the coating composition of the present
invention, the prepolymer of the present invention and a polymer
having a low heat decomposition temperature (hereinafter referred
to as a heat-decomposable polymer) are complexed, and at the time
of forming an insulation film, the heat decomposable polymer
portion is removed.
[0094] (b) A method wherein fine particles are added into the
coating composition of the present invention, and the fine particle
portions are removed during or after forming the insulation
film.
[0095] In the method (a), the heat decomposable polymer may, for
example, be an aliphatic polyether, an aliphatic polyester, an
acrylic polymer or a styrene polymer. The number average molecular
weight of the heat decomposable polymer is preferably from 1,000 to
100,000, more preferably from 1,000 to 50,000. When the molecular
weight is within this range, the compatibility with the prepolymer
of the present invention can be secured in the coating composition,
such being desirable. As a method for complexing the prepolymer of
the present invention and the heat decomposable polymer, a method
may, for example, be mentioned wherein a coating composition
comprising a prepolymer and the heat decomposable polymer will be
prepared and applied on a substrate, and then, the solvent is
evaporated and heat treatment is carried out to obtain a composite
film, or a method wherein the prepolymer and the heat decomposable
polymer are complexed by blocking or grafting, and the composite
thereby obtained is incorporated to the coating composition. As the
method for blocking or grafting, a known method may be employed.
For example, a method may be mentioned wherein a heat decomposable
polymer having a fluorinated aromatic ring or a phenolic hydroxyl
ring at its terminal, is prepared, and it is co-condensed at the
time of the condensation reaction for the preparation of the
prepolymer. The condensation reaction for the prepolymer will
proceed by the reaction mechanism of the above formula (2) or (3),
whereby the terminal fluorinated aromatic ring or phenolic hydroxyl
group moiety will be bonded to the prepolymer chain. Here, in a
case where the heat decomposable polymer has a fluorinated aromatic
ring or phenolic hydroxyl group at one terminal, it is possible to
obtain a prepolymer having the heat decomposable polymer grafted.
In a case where the heat decomposable polymer has a fluorinated
aromatic ring or phenolic hydroxyl group at each terminal, it is
possible to obtain a block product of the prepolymer and the heat
decomposable polymer.
[0096] The heat decomposable polymer has a low heat decomposition
temperature, and by the heating during the formation of an
insulation film, it is selectively decomposed and removed, and the
removed portions will be pores. It is possible to control the
porosity by the amount of the heat decomposable polymer added to
the coating composition, and the amount of the heat decomposable
polymer to be added, is usually preferably form 5 to 80 vol %, more
preferably from 10 to 70 vol %, based on the prepolymer.
[0097] In the method (b), the fine particles to be dispersed in the
coating composition of the present invention are preferably
inorganic fine particles. As such inorganic fine particles, fine
particles of silica, metal, etc. may be mentioned. The fine
particles will be dissolved and removed by e.g. acid treatment
after the film-forming, so that the removed portions will be pores.
It is possible to control the porosity by the amount of the fine
particles to be added. The amount of the fine particles to be added
is usually preferably from 5 to 80 vol %, more preferably from 10
to 70 vol %, based on the prepolymer.
[0098] The insulation film of the present invention may also be
preferably be complexed with another film. For example, in a case
where it is used as a passivation film for a semiconductor device
or as an interlayer insulation film for a semiconductor device, it
is preferred to form an inorganic film as a lower layer and/or
upper layer of the insulation film of the present invention.
[0099] The inorganic film may be formed by a normal pressure,
reduced pressure or plasma chemical vapor deposition (CVD) method
or a coating method and may, for example, be phosphorus and/or
boron doped, as the case requires, silicon oxide film so-called PSG
film or BPSG film, a silicon oxide film, a silicon nitride film, a
is silicon oxide nitride film, a SiOC film, or a spin-on-glass
(SOG) film.
[0100] By forming an inorganic film between the metal wiring and
the insulation film of the present invention, it is possible to
obtain effects to prevent peeling of the metal wiring and to
facilitate etching for e.g. a damascene structure. It is preferred
to form the inorganic film on the insulation film after partially
removing the insulation film of the present invention by an etch
back process or CMP (chemical mechanical polishing) process.
[0101] In a case where the adhesion between the insulation film and
the inorganic film is inadequate when the inorganic film is formed
on the insulation film of the present invention or film reduction
takes place at the time of forming the inorganic film, it is
preferred to apply the following method (I) or (II).
[0102] (I) A method of forming a multilayer inorganic film: In a
case where a silicon oxide film is formed by a plasma CVD process,
film reduction may occur depending upon the gas composition to be
used. In such a case, firstly, a thin inorganic film which
undergoes no film reduction (such as a silicon nitride film or a
normal pressure CVD-silicon oxide film, is formed. Then, using this
thin film as a barrier layer, a silicon oxide layer is formed.
[0103] (II) A method of treating the insulation film of the present
invention with energy rays: There is a case where the interface
adhesion in the inorganic film and the insulation film of the
present invention can be improved by treatment with energy rays.
Such energy ray treatment may, for example, be treatment by means
of electromagnetic waves in a broad sense including light, such as
ultraviolet irradiation, laser irradiation or microwave
irradiation, or treatment by means of electron rays such as
electron irradiation, glow discharge treatment, corona discharge
treatment or plasma treatment.
[0104] Among them, as a treating method suitable for a mass
production process for semiconductor devices, UV irradiation, laser
irradiation, corona discharge treatment or plasma treatment may be
mentioned.
[0105] Plasma treatment is more preferred since a damage to
semiconductor device is thereby little. The apparatus for the
plasma treatment is not particularly limited so long as a desired
gas can be introduced into the apparatus and an electric field can
be applied, and a commercially available barrel type or parallel
flat plate type plasma generating apparatus may suitably be used.
The gas to be introduced into the plasma apparatus is not
particularly limited so long as it is capable of effectively
activate the surface, and argon, helium, nitrogen, oxygen or a
mixed gas thereof may, for example, be mentioned. Further, as a gas
which is capable of activating the surface of the cured film for
the prepolymer and which brings about substantially no film
reduction, a mixed gas of nitrogen and oxygen, or a nitrogen gas
may be mentioned.
EXAMPLES
[0106] The present invention will be described in further detail
with reference to the following Examples and Comparative Examples.
However, the present invention is by no means thereby restricted.
Among the following Examples, Examples 1 to 6 and 10 to 14 are
Examples of the present invention, and Examples 7 to 9 are
Comparative Examples. Examples 1 to 9 are directed to preparation
of a prepolymer for evaluation of the basic properties of a cured
film; Example 10 is directed to evaluation of the adhesive property
of the cured film; Example 11 is directed to preparation of
pore-introduced cured film; Example 12 is directed to evaluation of
the properties of an insulation film; Example 13 is directed to
preparation of a film and evaluation of its properties; and Example
14 is directed to preparation of a prepolymer employing both (Y-1)
and (Y-2). Further, as the basic properties of the prepolymer in
each of Examples 1 to 9 and the cured film made of the prepolymer,
the respective items of the molecular weight, the relative
permittivity, the birefringence Tg and the thick film-forming
property were measured by the following methods.
Molecular Weight
[0107] A vacuum dried prepolymer was subjected to a gel permeation
chromatography method (GPC) to obtain a number average molecular
weight calculated as polystyrene. Tetrahydrofuran was used as the
carrier solvent.
Relative Permittivity
[0108] A vacuum dried prepolymer powder was dissolved in
cyclohexanone to obtain a 20% solution, which was filtered through
a PTFE filter having a pore diameter of 0.5 .mu.m. Using the
obtained solution, a cured film having a thickness of about 1 .mu.m
was formed by a spin coating method on a 4 inch silicon wafer. The
spinning conditions were 1,000 to 3,000 rpm for 30 seconds, and
after preheating by a hot plate at 100.degree. C. for 90 seconds
and 200.degree. C. for 90 seconds, heating was carried out in a
nitrogen atmosphere in a vertical furnace at 350.degree. C. for two
hours. Then, a CV measurement was carried out by a mercury prober
(SSM-495, manufactured by SSM) to obtain a relative permittivity at
1 MHz. As the thickness of the cured film, a value obtained by a
spectroellipsometer was used.
Birefringence
[0109] By the same method as described above, a cured film having a
thickness of from 2 to 5 .mu.m was formed on a quartz substrate to
prepare a slab optical waveguide. The heating conditions were
300.degree. C. for one hour. By a prism coupler (model 2010)
manufactured by Metricon Corporation, refractive indices against
the polarized light in a perpendicular direction and the polarized
light in a horizontal direction to the film surface, were,
respectively measured, and their difference was obtained. Here, the
measurement was carried out at a wavelength of light being 1,550
nm.
Tg
[0110] The above-mentioned 20% prepolymer solution in cyclohexanone
obtained by filtration was dropped on a silicon wafer, and after
preheating at 200.degree. C. for 300 seconds by a hot plate,
heating was carried out in a nitrogen atmosphere at 350.degree. C.
for one hour in a vertical furnace to obtain a cured film. The film
was scraped off from the silicon wafer, and DSC measurement was
carried out to obtain Tg. In the DSC measurement, scanning was
carried out in a nitrogen atmosphere of from 40.degree. C. to
400.degree. C. under a condition of a temperature raising rate of
10.degree. C./min.
Thick Film-Forming Property
[0111] A vacuum dried prepolymer powder was dissolved in
cyclohexanone to obtain a 40% solution, which was spin-coated on a
silicon wafer, followed by heating at 250.degree. C. for 180
seconds by a hot plate to form a cured film having a thickness of
about 10 .mu.m. The presence or absence of defects in the cured
film was evaluated by visual inspection and observation by
metallographic microscope.
Example 1
Preparation of Prepolymer by the Method (i) Using Compounds (B),
(C) and (Y-1)
[0112] Into a 100 mL pyrex (registered trademark) four-necked flask
equipped with a Dimroth condenser, a thermocouple thermometer and a
mechanical stirrer, 2.67 g of perfluorobiphenyl as the compound
(B), 0.50 g of 1,3,5-trihydroxybenzene as the compound (C) and 28 g
of N,N-dimethylacetamide (hereinafter referred to as DMAc) were
charged with stirring, the mixture was heated on an oil bath, and
when the liquid temperature became 60.degree. C., 3.0 g of
potassium carbonate was quickly added, followed by heating at
60.degree. C. for 4 hours with continuous stirring. Then, a
solution having 0.85 g of 4-(4-fluorophenylethynyl)phenol as the
compound (Y-1) dissolved in 6 g of DMAc, was added, followed by
further heating at 60.degree. C. for 5 hours.
[0113] Then, the reaction solution was cooled to room temperature
and gradually put into about 200 mL of vigorously stirred 0.5 N
aqueous hydrochloric acid solution, whereby a slightly brown
powdery substance precipitated. This slightly brown powdery
substance was collected by filtration and washed five times with
pure water, followed by vacuum drying at 80.degree. C. for 15 hours
to obtain 3.4 g of a whitish gray powdery prepolymer. The obtained
prepolymer had ether bonds and ethynyl groups as the crosslinkable
functional groups (A), and its molecular weight was 9,000. A cured
film formed by the above described method using the prepolymer had
a relative permittivity of 2.6 and a birefringence of 0.002. By the
DSC measurement, no transition point or no heat generation/heat
absorption peak was observed, and Tg was at least 400.degree. C. In
the evaluation of the thick film forming property, defects such as
cracks were not observed.
Example 2
Preparation of Prepolymer by the Method (ii) Using the Compounds
(B), (C) and (Y-2)
[0114] Into a 100 mL pyrex (registered trademark) four-necked flask
equipped with a Dimroth condenser, a thermocouple thermometer and a
mechanical stirrer, 0.57 g of pentafluorophenylacetylene as the
compound (Y-2), 0.71 g of 1,3,5-trihydroxybenzene as the compound
(C) and 3.0 g of DMAc were charged. With stirring, the mixture was
heated on an oil bath, and when the liquid temperature became
60.degree. C., 0.4 g of potassium carbonate was quickly added,
followed by heating at 60.degree. C. for 5 hours with continuous
stirring. Then, a solution having 3.00 g of perfluorobiphenyl as
the compound (B) dissolved in 37.8 g of DMAc, was added, and then
3.1 g of potassium carbonate was added. The mixture was heated
further at 60.degree. C. for 17 hours.
[0115] Then, the reaction solution was cooled to room temperature
and gradually put into about 200 mL of vigorously stirred 0.5 N
aqueous hydrochloric acid solution, whereby a slightly brown
powdery substance precipitated. This slightly brown powdery
substance was collected by filtration and further washed twice with
pure water followed by vacuum drying at 80.degree. C. for 15 hours
to obtain 3.5 g of a whitish gray powdery prepolymer. The obtained
prepolymer had ether bonds and ethynyl groups. The same evaluation
as in Example 1 was carried out, and results of evaluation of basic
properties are shown in Table 1.
Example 3
Preparation of Prepolymer by the Method (ii) Using the Compounds
(B), (C) and (Y-2)
[0116] A prepolymer powder was obtained in the same manner as in
Example 2 except that 0.58 g of pentafluorostyrene was used instead
of 0.57 g of pentafluorophenylacetylene as the compound (Y-2). The
obtained prepolymer had ether bonds and vinyl groups. Evaluation
was carried out in the same manner as in Example 1, and the results
of the evaluation of the basic properties are shown in Table 1.
Example 4
Preparation of Prepolymer by the Method (ii) Using the Compounds
(B), (C) and (Y-2)
[0117] Into a 50 mL two-necked flask equipped with a Dimroth
condenser and a stirrer chip, 0.57 g of pentafluoroacetylene as the
compound (Y-2), 0.75 g of 1,3,5-trihydroxybenzene as the compound
(C), 3.00 g of perfluorobiphenyl as the compound (B) and 38.97 g of
DMAc were charged. With stirring, the mixture was heated to
60.degree. C. on an oil bath, and 3.72 g of potassium carbonate was
quickly added, followed by heating at 60.degree. C. for 22 is hours
with continuous stirring.
[0118] Then, the reaction solution was cooled to room temperature
and gradually put into 150 mL of a vigorously stirred 0.5 N
hydrochloric acid aqueous solution, whereby a slightly brown
powdery substance precipitated. This slightly brown powdery
substance was collected by filtration and washed twice with pure
water, followed by vacuum drying at 80.degree. C. for 12 hours to
obtain 3.10 g of a whitish gray powdery prepolymer. The obtained
prepolymer had ether bonds and ethynyl groups. Evaluation was
carried out in the same manner as in Example 1, and the results of
the evaluation of the basic properties are shown in Table 1.
Example 5
Preparation of Prepolymer by the Method (ii) Using the Compounds
(B), (C) and (Y-2)
[0119] Into a 50 mL two-necked flask equipped with a Dimroth
condenser and a stirrer chip, 1.15 g of pentafluorophenylacetylene
as compound (Y-2), 0.65 g of 1,3,5-trihydroxybenzene as the
compound (C), 2.00 g of perfluorobiphenyl as the compound (B) and
34.22 g of DMAc were charged. With stirring, the mixture was heated
to 60.degree. C. on an oil bath, and 3.23 g of potassium carbonate
was quickly added, followed by heating at 60.degree. C. for 22
hours with continuous stirring.
[0120] Then, the reaction solution was cooled to room temperature
and gradually put into 150 mL of a vigorously stirred 0.5 N
hydrochloric acid aqueous solution, whereby a slightly brown
powdery substance precipitated. This slightly brown powdery
substance was collected by filtration and washed twice with pure
water, followed by vacuum drying at 80.degree. C. for 12 hours to
obtain 2.58 g of a whitish gray powdery prepolymer. The obtained
prepolymer had ether bonds and ethynyl groups. Evaluation was
carried out in the same manner as in Example 1, and the results of
the evaluation of the basic properties are shown in Table 1.
Example 6
Preparation of Prepolymer by the Method (ii) Using the Compounds
(B), (C) and (Y-2)
[0121] A prepolymer powder was obtained in the same manner as in
Example 5 except that 1.83 g of 1,3,5-tris(4-hydroxyphenyl)benzene
was used instead of 0.65 g of 1,3,5-trihydroxybenzene as the
compound (C). The obtained prepolymer had ether bonds and ethynyl
groups. Evaluation was carried out in the same manner as in Example
1, and the results of evaluation of the basic properties are shown
in Table 1.
Example 7 (Comparative Example)
Preparation of Known Prepolymer
[0122] A 100 mL pyrex (registered trademark) four-necked flask
equipped with a Dimroth condenser, a thermocouple thermometer and a
mechanical stirrer, was flushed with nitrogen, and then, 2.51 g of
perfluorobiphenyl, 1.68 g of
dihydroxy-2,2-diphenylhexafluoropropane, 40 g of DMAc and 5 g of
toluene were charged, and further, 1.66 g of potassium carbonate
was charged. With stirring, the mixture was heated at 120.degree.
C. for 5 hours on an oil bath, and then, 0.7 g of potassium
carbonate and 1.05 g of phenyl ethyl phenol were put, followed by
further heating at 120.degree. C. for 3 hours.
[0123] The reaction solution was cooled to room temperature and
gradually put into 500 mL of a vigorously stirred mixed solution of
pure water/methanol (volume ratio: about 1/1) containing 8 g of
acetic acid, whereby a slightly brown powdery substance
precipitated. This slightly brown powdery substance was collected
by filtration and washed five times with pure water, followed by
vacuum drying at 80.degree. C. for 15 hours to obtain 4.2 g of a
slightly brown powdery prepolymer. Evaluation was carried out in
the same manner as in Example 1, and the results of the evaluation
of the basic properties are shown in Table 1.
Example 8 (Comparative Example)
Preparation of Known Prepolymer
[0124] Into a 2 L pyrex (registered trademark) four-necked flask
equipped with a Dimroth condenser, a thermocouple thermometer and a
mechanical stirrer, 14.45 g of pentafluorophenylacetylene, 13.44 g
of 1,3,5-trihydroxybenzene and 250.95 g of DMAc were charged. With
stirring, the mixture was heated on an oil bath, and when the
liquid temperature became 60.degree. C., 10.39 g of potassium
carbonate was quickly added, followed by heating at 60.degree. C.
for 2.5 hours with continuous stirring. Then, a solution having 79
g of perfluoro(1,3,5-triphenylbenzene) dissolved in 711 g of DMAc,
was added, and then, 55.87 g of potassium carbonate was added,
followed by further heating at 60.degree. C. for 14.5 hours.
[0125] Then, the reaction solution was cooled to room temperature
and gradually put into about 3 L of a vigorously stirred 0.5 N
hydrochloric acid aqueous solution, whereby a white powdery
substance precipitated. This white powdery substance was collected
by filtration and washed three times with pure water, followed by
vacuum drying at 80.degree. C. for 15 hours to obtain 91.8 g of a
white powdery prepolymer. The obtained prepolymer had ether bonds
and ethynyl groups. Evaluation was carried out in the same manner
as in Example 1, and the results of the evaluation of the basic
properties are shown in Table 1.
Example 9 (Comparative Example)
Preparation of Known Prepolymer
[0126] In accordance with the method disclosed in Example 8 of
JP-A-10-247646, a prepolymer was prepared from perfluorobiphenyl
and 1,3,5-trihydroxybenzene. Evaluation was carried out in the same
manner as in Example 1, and the results of the evaluation of the
basic properties are shown in Table 1. TABLE-US-00001 TABLE 1 Thick
film- Molecular Relative Bi- Tg forming weight permittivity
refringence (.degree. C.) property 1 9,000 2.6 0.002 >400 No
defect 2 4,000 2.5 -- >400 No defect 3 4,000 2.4 -- -- No defect
4 8,300 2.4 0.001 >400 No defect 5 3,300 2.5 0.001 >400 No
defect 6 4,000 2.6 -- >400 -- 7 5,100 2.8 0.008 295 No
Comparative defect 8 5,500 2.4 0.001 >400 Cracks Comparative
observed 9 10,000 2.5 -- 220 -- Comparative
[0127] From the results in Table 1, the prepolymers of the present
invention were found to have a low permittivity, a low
birefringence, high Tg and a thick film-forming property
simultaneously and thus is useful for insulation films and optical
materials.
Example 10
Adhesive Property of a Cured Film with a Substrate
[0128] A part of a 20% solution of the prepolymer obtained in
Example 4 in cylohexanone (hereinafter referred to as the solution
4) was taken out and aminophenyltrimethoxysilane was added in an
amount of 2 mass % based on the prepolymer to obtain a solution
4-1. Further, instead of aminophenyltrimethoxysilane,
3-aminopropyltriethoxysilane was added in an amount of 1 mass %
based on the prepolymer to obtain a solution 4-2. Then, on silicon
wafers, the solution 4, the solution 4-1 and the solution 4-2 were
applied by spin coating to form wet films, followed by heating to
prepare cured films.
[0129] The rotational speed of the spin coating was adjusted so
that the wet film thickness became 500 nm, and after preliminary
heating by a hot plate at 100.degree. C. for 90 seconds and at
200.degree. C. for 90 seconds, heating was carried out in a
nitrogen atmosphere at 350.degree. C. for two hours by a vertical
furnace. These samples were subjected to a pressure cooker test
(121.degree. C., 100% RH, 4 hours) in a chamber supplied by ETAC,
and then the adhesive properties of the cured films with the
substrate were evaluated by the cross cut tape peel test as
disclosed in JIS D0202.
[0130] At least 80% of cross cut sections of the cured film
obtained from the solution 4 was peeled.
[0131] Whereas, no peeling was observed with respect to cross cut
sections of the cured films obtained from the solutions 4-1 and
4-2.
[0132] From this Example, an adhesion promoter such as an
aminosilane was found to be effective for the improvement of the
adhesive property of the cured film.
Example 11
Preparation of a Cured Film Containing Pores
[0133] To the 20% solution of the prepolymer prepared in Example 5
in cyclohexanone, a poly(.epsilon.-caprolactone) having a number
average molecular weight of 3,000 was added in an amount of 25 mass
% based on the prepolymer and dissolved, followed by filtration by
a PTFE filter (pore diameter: 0.2 .mu.m) to obtain a uniform
transparent solution (hereinafter referred to as the solution 5).
The solution 5 was spin-coated on a 4-inch silicon wafer and then
heated to form a cured film. The spinning conditions were 2,500 rpm
for 30 seconds, and in the same manner as in Example 10, preheating
was followed by heating. The cross section of the cured film was
observed by SEM, whereby the presence of fine pores of nanometer
order was confirmed. The relative permittivity of the cured film
was 1.8. Further, no peeling by a cross cut tape peel test or no
breakage of the film was observed.
Example 12
Evaluation as an Interlayer Insulation Film
[0134] From the solution 4, the solution 4-1 and the solution 5, a
stack of films of a silicon wafer/p-SiO (300 nm)/prepolymer
insulation film (500 nm)/p-SiN (50 nm)/p-SiO(500 nm) was prepared
by the following method.
[0135] On a 4-inch silicon wafer having a p-SiO film (film
thickness: 300 nm) formed, the solution was spin-coated to form a
prepolymer insulation film having a thickness of 500 in the same
manner as in Example 10. Then, by a mixed glass of monosilane,
ammonia and nitrogen, a silicon nitride film was formed in a
thickness of 50 nm, and then, by a mixed glass of monosilane and
oxygen dinitride, a silicon oxide film having a thickness of 500 nm
was formed.
[0136] The obtained stack was heated at 350.degree. C. for 60
minutes in a nitrogen atmosphere, whereby the resistance against
cracking due to heat stress was investigated by a metallographic
microscope. The results are shown below.
[0137] With the stack formed from the solution 4, no formation of
cracks or other defects was observed. With the stack formed from
the solution 4-1, no formation of cracks or other defects was
observed.
[0138] With the stack formed from the solution 5, no formation of
cracks or other defects was observed.
[0139] From this Example, the prepolymer of the present invention
was found to be easy for stacking with an inorganic film and thus
is excellent in applicability as an interlayer insulation film.
Example 13
Preparation and Evaluation of a Prepolymer Film
[0140] A 40% solution of the prepolymer obtained in Example 4 in
cyclohexanone was spin-coated on a silicon wafer, and then, after
preheating by a hot plate at 100.degree. C. for 180 seconds and at
200.degree. C. for 180 seconds, heating was carried out in a
nitrogen atmosphere at 300.degree. C. for one hour by an oven.
[0141] From the silicon wafer, the cured film was peeled off to
obtain a flexible slightly brown film having a thickness of 20
.mu.m. By means of a TG-DTA apparatus manufactured by MacScience,
TG (thermogravimetry) measurement was carried out in a nitrogen
atmosphere at a temperature raising rate of 10.degree. C./min,
whereby a 5% weight reduction temperature of this film was about
470.degree. C. By means of a moisture absorption/desorption
measuring apparatus (IGASORP) manufactured by SiberHegner Company,
Ltd., the moisture absorption was measured at 85.degree. C. under a
relative humidity of 85% and found to be 0.2%. A strip sample of 5
mm.times.15 mm was cut out, and by means of TMA apparatus
manufactured by MacScience, the linear expansion coefficient from
room temperature to 200.degree. C. was measured under conditions of
the tensile load being 5 g and the temperature raising rate being
10.degree. C./min and was found to 55 ppm. From this Example, it
was found possible to obtain a film having high heat resistance,
low water absorption and a low thermal expansion coefficient by
using the prepolymer of the present invention.
Example 14
Preparation of Prepolymer Using the Compounds (B), (C), (Y-1) and
(Y-2)
[0142] Into a 50 mL two-necked flask equipped with a Dimroth
condenser and a stirrer chip, 0.57 g of pentafluorophenylacetylene
as the compound (Y-2), 0.75 g of 1,3,5-trihydroxybenzene as the
compound (C), 3.00 g of perfluorobiphenyl as the compound (B) and
38.97 g of DMAc are charged. With stirring, the mixture is heated
to 60.degree. C. on an oil bath, and 3.72 g of potassium carbonate
is quickly added, followed by heating at 60.degree. C. for 18 hours
with continuous stirring. Then, 0.35 g of 3-ethynylphenol is added
as the compound (Y-1), and heating is further continued for 5 hours
at 60.degree. C.
[0143] Then, the reaction solution is cooled to room temperature
and gradually put into 150 mL of vigorously stirred 0.5 N nitric
acid aqueous solution, whereby a precipitate of a slightly brown
powdery substance is formed. This precipitate is collected by
filtration and washed twice with pure water, followed by vacuum
drying at 80.degree. C. to obtain a whitish gray powdery
prepolymer. Using the obtained prepolymer, the basic properties are
evaluated in the same manner as in Example 1, whereby substantially
the same results as in Example 1 are obtained.
[0144] The entire disclosure of Japanese Patent Application No.
2003-340031 filed on Sep. 30, 2003 including specification, claims
and summary is incorporated herein by reference in its
entirety.
* * * * *