JP2000256550A - Coating solution for insulating film formation - Google Patents

Abstract

(57) Abstract: Provided is an insulating film forming coating liquid capable of forming a thermosetting insulating film having a relative dielectric constant of 2.7 or less on various substrates including electronic devices. The insulation includes a polyether resin having at least one structural unit selected from the structural units represented by the following general formula (1) and having a structure represented by the general formula (2) at a terminal of a resin chain. Coating solution for film formation. (R ^{1 to} R ⁴ are each independently a hydrogen atom, a fluorine atom,
It represents a substituent selected from a fluorine-substituted alkyl group having 1 to 6 carbon atoms and a fluorine-substituted cycloalkyl group having 4 to 8 carbon atoms, all of which are not hydrogen atoms. ) (R ⁵ has 2 to 4 carbon atoms and represents a functional group having a carbon-carbon double bond or a carbon-carbon triple bond. P represents an integer of 0 or more and 1 or less.)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating solution for forming an insulating film. More specifically, the present invention relates to a coating liquid for forming an insulating film on various substrates including electronic devices, which has a low dielectric constant and is excellent in heat resistance. .

[0002]

2. Description of the Related Art Higher speed of an LSI is achieved by miniaturization of a transistor constituting the LSI. In recent years, as wiring intervals have been reduced due to this miniaturization, delays in signals transmitted through the wiring (wiring delay) and crosstalk between adjacent wirings have become remarkable, which is a serious problem that hinders high performance of the LSI itself. There is concern that it will become.

As a method for solving this problem, it has been studied to lower the relative dielectric constant of an insulating film filling the space between wirings. Conventionally, SOG (Spin o) used as an insulating film
n Glass) film is an effective method as a manufacturing process because an insulating film can be easily formed on a device substrate by coating and baking, but its relative dielectric constant is 2.8 to 3.9, It cannot be said that it is a relative dielectric constant. Wiring distance is 0.1
When the thickness is 8 μm or less, an insulating film having a relative dielectric constant of 3.0 or less, more preferably 2.5 or less is required. From this viewpoint, it has been studied to use an organic resin film as an insulating film to lower the dielectric constant. However, the conventional insulating film has a disadvantage that it is deformed by heat treatment.

[0004]

SUMMARY OF THE INVENTION Under such circumstances, an object of the present invention is to form a thermosetting insulating film having a relative dielectric constant of 2.7 or less on various substrates including electronic devices. To provide a coating liquid for forming an insulating film.

[0005]

That is, the present invention provides:
[1] An insulating film having at least one structural unit selected from the structural units represented by the following general formula (1) and including a polyether resin having a structure represented by the general formula (2) at a resin chain terminal It relates to a coating liquid for formation.

(R ^{1 to} R ⁴ are each independently a hydrogen atom,
It represents a substituent selected from a fluorine atom, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, and a fluorine-substituted cycloalkyl group having 4 to 8 carbon atoms, all of which are not hydrogen atoms. ) (R ⁵ has 2 to 4 carbon atoms and represents a functional group having a carbon-carbon double bond or a carbon-carbon triple bond. P represents an integer of 0 or more and 1 or less.)

Further, the present invention relates to [2] a coating liquid for forming an insulating film, comprising the polyether resin described in [1] and an organic solvent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyether resin according to the present invention has at least one structural unit represented by the above general formula (1) in a resin chain, and further has a resin chain terminal group represented by a general formula (2). It is preferably a polyether resin having a structure to be dissolved in a solvent.

In the general formula (1), R ^{1 to} R ⁴ are each independently capable of lowering the relative dielectric constant by introducing a fluorine atom or a functional group containing a fluorine atom. 0.7 or less can be obtained. Specifically, R ^{1 to} R ⁴ are each independently a substituent selected from a hydrogen atom, a fluorine atom, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, and a fluorine-substituted cycloalkyl group having 4 to 8 carbon atoms. Yes, not all are hydrogen atoms. Here, the fluorine-substituted alkyl group and the fluorine-substituted cycloalkyl group are, for example, a difluoromethyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a nonafluorobutyl group,
Tridecafluorohexyl group, tris (trifluoromethyl) methyl group, perfluorooctyl group, 1,1,1
An alkyl group or a cycloalkyl group in which a hydrogen atom is substituted with a fluorine atom, such as a tris (pentafluoroethyl) methyl group, a nonafluorocyclopentane group, an undecafluorocyclohexyl group, and the like.

Further, it is soluble in solvents, especially alcohol solvents such as methanol, isopropanol and n-butanol which are organic solvents generally used in the technical field; ketone solvents such as 2-heptanone and methyl isobutyl ketone; butyl acetate , Isobutyl acetate, ethyl lactate,
In order to improve the solvent solubility in ester solvents such as γ-butyrolactone; alkylene glycol derivative solvents such as propylene glycol monomethyl ether acetate and 1,2-dimethoxyethane, a functional group for maintaining plasticity is introduced before curing. Or a method of increasing the affinity with a solvent molecule. Specifically, as the polyether resin in the present invention, a resin having a structural unit represented by the general formula (3) is preferably used.

Here, R ^{6 to} R ⁹ each independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, a cycloalkyl group having 4 to 8 carbon atoms or A substituent selected from a fluorine-substituted alkyl group having 1 to 8 carbon atoms is shown. A represents a methylene group, a 2,2-isopropylidene group, a 1,1
-A cyclopentyl group, a 1,1-cyclohexyl group, a phenylmethylene group, a 1,1-phenylethylene group are preferably used, and an ether group or a sulfone group is preferably used as a linking group for improving affinity with a solvent. .

A polyether resin in which at least one of R ^{1 to} R ⁴ in the general formula (3) is a fluorine atom is particularly advantageous in production. This makes it possible to easily synthesize a polyether resin from a trifluorobenzene derivative, a tetrafluorobenzene derivative, a pentafluorobenzene derivative, or hexafluorobenzene. That is, a polyether resin can be easily synthesized by condensing bisphenols with an alkali catalyst. Particularly, hexafluorobenzene is easily available industrially and is preferably used. By using hexafluorobenzene in the polyether resin having the structural unit represented by the general formula (3), the general formula (4)
Can be obtained.

In the terminal group represented by the general formula (2),
R ⁵ is preferably a vinyl group or an allyl group because of good curability. In order to introduce this terminal group, a desired functional group can be introduced into the resin terminal by, for example, o-allylphenol, p-allylphenol, p-hydroxystyrene, p-vinylbenzyl chloride or the like. The alkenyl group remaining in the uncured functional group deteriorates the relative dielectric constant, so that it is necessary to surely cure the alkenyl group. These functional groups can be cured by a heat treatment at 150 to 300 ° C., but a curing catalyst can be used if necessary. Examples of the curing catalyst include organic peroxides such as t-butyl peroxide, di-t-butyl peroxide, dibenzoyl peroxide, dicumyl peroxide, cumylbenzoyl peroxide, and the like. Is preferably used because it is vaporized and removed from the insulating film itself. 0.001-1% based on polyether resin as curing catalyst
Is used. If the amount is less than 0.001%, the catalytic activity decreases, and the curing rate decreases. On the other hand, if the amount exceeds 1%, foaming in the formed insulating film becomes remarkable, and undesired phenomena such as film peeling occur. .

Further, at the stage of effecting by heat treatment, an appropriate coupling agent can be used to improve the adhesion. As a preferable coupling agent, vinyl triethoxy silane, methacryl triethoxy silane, mercaptoethyl triethoxy silane, or the like which reacts with the terminal group represented by the general formula (2) is preferably used.

Further, the coating liquid for forming an insulating film of the present invention comprises:
It is characterized by containing the polyether resin and an organic solvent, as the organic solvent, an alcohol solvent such as methanol, isopropanol and n-butanol; a ketone solvent such as 2-heptanone and methyl isobutyl ketone; butyl acetate and acetic acid Ester solvents such as isobutyl, ethyl lactate and γ-butyrolactone; and alkylene glycol derivative solvents such as propylene glycol monomethyl ether acetate and 1,2-dimethoxyethane.

Further, as a method for lowering the dielectric constant, another resin having a fluorine-substituted alkyl group in the main chain or side chain of the polymer can be blended. That is, as commercially available products, for example, Neoflon FEP, Polyflon TFE
Organic solvent-dispersed resin such as Teflon J (manufactured by Mitsui Fluorochemicals Co., Ltd.), Lumiflon (manufactured by Asahi Glass Co., Ltd.), Cefral Coat (Central Glass Co., Ltd.)
) Can be reduced by adding a fluorine resin soluble in the organic solvent described above.

The coating liquid for an insulating film of the present invention is applied on a substrate by a spin coating method or a dipping method and the like.
By pre-baking at 250C and performing heat treatment at 250C to 450C, an insulating film having a relative dielectric constant of 2.7 or less and no thermal deformation can be formed.

[0018]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention. Synthesis Example 1 Perfluorobenzene 1 in a 500 ml four-necked flask
9.6 g (105 mmol), bisphenol A21.
8 g (75 mmol), 1.3 g of o-allylphenol
(10 mmol), 36.2 g of potassium carbonate (262 m
mol) and 196 g of dimethylformamide, the internal temperature was raised to 85 ° C., and the mixture was stirred at the same temperature for 6 hours. After the completion of the reaction, the precipitated inorganic salt was separated by filtration. The obtained filtrate was dropped into 1 liter of deionized water to precipitate a resin.
After filtering the obtained resin, it was again dispersed in 300 ml of deionized water, and acetic acid was added until the pH of the dispersion reached 3.0. Next, the crystals were filtered, washed with deionized water, and washed with methanol, and then at 40 ° C. for 5 hours.
Vacuum drying was performed to obtain 36.7 g of a resin cake. This is designated as resin A.

Synthesis Example 2 17.1 g (75 mmol) of charged bisphenol A
l), 4.1 g (31 mm) of charged o-allylphenol
ol), the same processing as in Synthesis Example 1 was performed,
34.7 g of a resin cake was obtained. This is called resin B.

Examples 1-2 The resin cake obtained in the synthesis example was dissolved in propylene glycol monomethyl ether acetate so as to have a solid content of 15%, and t-butyl peroxide was further reduced to 0.01% based on the resin. It was added so that it might become. Then 0.2μm
The mixture was filtered with a filter to prepare a coating solution. The obtained coating liquid is applied to a 4-inch silicon wafer at a rotation speed of 2500 rpm.
Spin coating (Mikasa spinner 1H-360 type)
And baked at 150 ° C,
A coating film was formed by baking for 0 minutes. The film thickness is measured using an optical film thickness meter (Nano Spec 21 manufactured by Nanometric Corporation).
0). The presence or absence of cracks was observed with an optical microscope at a magnification of 50 times. The relative permittivity was measured at a frequency of 1 MHz by a mercury probe method (Japanese SSM 495). As described above, thermal curing is performed by applying and baking a wafer in which a 1.2 μm thick SiO ₂ film is patterned at 0.5 μm intervals to obtain a cured film, and then performing a heat treatment at 400 ° C. for 30 minutes under a nitrogen stream. After the film deformation before and after the heat treatment at 400 ° C. was performed by Pd vapor deposition, the cross section was observed with an SEM (Hitachi S-4700). Table 1 shows the results.

[0021]

[Table 1]

[0022]

As described above, the coating liquid for forming an insulating film of the present invention can form a thermosetting insulating film having a relative dielectric constant of 2.7 or less on various substrates including electronic devices. Great industrial value.

Claims (6)

[Claims] An insulating film having at least one structural unit selected from the structural units represented by the general formula (1) and containing a polyether resin having a structure represented by the general formula (2) at a terminal of a resin chain. Forming coating solution. (R ^{1 to} R ⁴ are each independently a hydrogen atom, a fluorine atom,
It represents a substituent selected from a fluorine-substituted alkyl group having 1 to 6 carbon atoms and a fluorine-substituted cycloalkyl group having 4 to 8 carbon atoms, all of which are not hydrogen atoms. ) (R ⁵ has 2 to 4 carbon atoms and represents a substituent having a carbon-carbon double bond or a carbon-carbon triple bond. P represents an integer of 0 or more and 1 or less.) 2. The coating liquid for forming an insulating film according to claim 1, wherein the polyether resin has a structural unit represented by the general formula (3). (R ^{1 to} R ⁴ are as defined in claim 1. R ^{6 to} R ⁹ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, Carbon number 4 ~
And a substituent selected from 8 cycloalkyl groups or fluorine-substituted alkyl groups having 1 to 8 carbon atoms. A is a methylene group,
2,2-isopropylidene group, 1,1-cyclopentyl group, 1,1-cyclohexyl group, phenylmethylene group,
It represents at least one selected from a 1,1-phenylethylene group, an ether group and a sulfone group. ) 3. The coating liquid for forming an insulating film according to claim 1, wherein at least one of R ^{1 to} R ⁴ is a fluorine atom. 4. The method according to claim 1, wherein R ^{1 to} R ⁴ are all fluorine atoms.
4. The coating liquid for forming an insulating film according to any one of items 1 to 3. 5. In the terminal group represented by the general formula (2),
The coating liquid for forming an insulating film according to claim 1, wherein R ⁵ is a vinyl group or an allyl group. 6. A coating liquid for forming an insulating film, comprising the polyether resin according to claim 1 and an organic solvent.