Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-06-27
2002-04-30
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S180000, C521S184000
Reexamination Certificate
active
06380271
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a material for electrical insulating organic film, superior in electrical properties, thermal properties, mechanical properties and physical properties; to an electrical insulating organic film made from the material; and to a process for producing such an electrical insulating organic film. This electrical insulating organic film can be used in semiconductor applications such as interlayer dielectric and protective film for semiconductor, interlayer dielectric for multilayer circuit, cover coat for flexible copper-clad laminate, solder resist film, liquid crystal-aligning film and the like.
DESCRIPTION OF RELATED ART
A variety of materials for semiconductor such as inorganic materials, organic materials and the like are in use in various applications, depending upon the properties required for them in the applications. As, for example, the interlayer dielectric for semiconductor, there is used an inorganic insulating film such as silicon dioxide formed by chemical vapor deposition. Such an inorganic film (e.g. silicon dioxide), however, has problems in high dielectric constant, high water absorption, etc. because, in recent years, semiconductor devices have come to possess higher functions and higher performances. As one means for alleviating the problems, use of an organic material is being investigated.
As the organic material for semiconductor applications, there is mentioned a polyimide resin superior in heat resistance, mechanical properties, etc.; and this resin is used in solder resist, cover lay, liquid crystal-aligning film, etc. The polymide resin, however, generally has problems in electrical properties and water absorption resistance because it has two carbonyl groups in the imide ring. To alleviate these drawbacks, it was attempted to introduce fluorine or trifluoromethyl group into the polyimide for improvement in electrical properties, water it absorption resistance and heat resistance; however, the attempt has not responded to the current requirements.
Hence, it is being attempted to use, as an insulating material for semiconductor applications, a polybenzoxazole resin superior to the polyimide resin in electrical properties and water absorption resistance. Polybenzoxazole resins easily satisfy only one of electrical properties, thermal properties or physical properties. For example, a polybenzoxazole resin composed of 4,4-diamino-3,3′-dihydroxybiphenyl and terephthalic acid has heat resistance (e.g. very high resistance to thermal decomposition and high Tg) but does not satisfy electrical properties (e.g. dielectric constant and dielectric loss tangent); and a polybenzoxazole resin composed of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and terephthalic acid shows good electrical properties (e.g. low dielectric constant) but does not satisfy heat resistance or the like. In recent years, a material of low dielectric constant has been desired which shows a dielectric constant lower than 2.5; however, no resin is developed yet which satisfies this requirement and further is superior in other electrical properties, thermal properties and physical properties.
Introduction of air (dry air has a dielectric constant of 1) into a resin to make lower the dielectric constant of the resin can be inferred from the technique for producing a foamed polymer having pores of about 20 microns in average diameter, described in U.S. Pat. No. 3,883,452 (Scheuerlein et al., issued on May 13, 1975). In order to obtain an effective insulating material by introducing air into a resin, however, it is necessary that the insulating material obtained has fine pores of submicron order and show a uniform dielectric constant.
As to the technique for obtaining fine pores of submicron order, U.S. Pat. No. 5,776,990 (Hedrick et al., issued on Jul. 7, 1998) discloses a process which comprises subjecting a block copolymer to phase separation of submicron order and heat-decomposing the heat-decomposable block component to form a resin having fine pores of submicron order. That a block copolymer can be subjected to phase separation in submicron order, is known [T. Hashimoto, M. Shibayama, M. Fujimura and H. Kawai, “Microphase Separation and the Polymer-Polymer Interphase in Block Polymers” in “Block Copolymers-Science and Technology”, p. 63-108, edited by D. J. Meier (Harwood Academic Pub., N.Y., 1983)]. Further, that polymers having a low ceiling temperature decompose easily, is generally well known in the field of polymer science. However, in order to obtain a resin composition having fine pores and yet being satisfactory in dielectric constant, mechanical properties, electrical properties, water absorption resistance and heat resistance, there is a large restriction in selection of the resin, block polymerization technique and heat-decomposable component used, and no resin composition satisfactory in all of these properties is developed yet.
OBJECT AND SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the prior art, the present inventors made an extensive study with an aim of providing a material for electrical insulating organic film superior in all of electrical properties, thermal properties and physical properties, an electrical insulating organic film made of the above material, and a process for producing such an electrical insulating organic film.
As a result, the present inventors found out that an electrical insulating organic film having fine pores, consisting of a layer of a polybenzoxazole resin having a structure represented by the following general formula (1), is low in dielectric constant and further superior in other electrical properties, thermal properties and physical properties, and thus the present invention has been completed based on the above finding:
wherein n is an integer of 2 to 1,000; X is a tetravalent organic group; and Y is a bivalent organic group.
The present invention provides an electrical insulating organic film, a material for electrical insulating organic film, and a process for producing an electrical insulating organic film, each shown in one of the following (1) to (5).
(1) An electrical insulating organic film having fine pores, consisting of a layer of a polybenzoxazole resin having a structure represented by the general formula (1).
(2) A material for electrical insulating organic film, obtained by mixing a polybenzoxazole precursor or a polybenzoxazole resin with an oligomer.
(3) A material for electrical insulating organic film, obtained by reacting at least one carboxylic acid terminal of a polybenzoxazole precursor, with an amino group- or hydroxyl group-containing oligomer.
(4) A process for producing an electrical insulating organic film, which comprises mixing a polybenzoxazole recursor or a polybenzoxazole resin with an oligomer, forming a film from the resulting mixture, and heating the film to give rise to thermal decomposition and gasification of the oligomer, to obtain a polybenzoxazole resin layer having fine pores.
(5) A process for producing an electrical insulating organic film, which comprises reacting at least one carboxylic acid terminal of a polybenzoxazole precursor with an amino group- or hydroxyl group-containing oligomer to synthesize a material for electrical insulating organic film, forming a film from the material, heating the film to give rise to ring closure of the polybenzoxazole precursor, further heating the resulting material to give rise to thermal decomposition and gasification of the oligomer group, to obtain a polybenzoxazole resin layer having fine pores.
DETAILED DESCRIPTION OF THE INVENTION
The first material for electrical insulating organic film according to the present invention is obtained by uniform mixing of a polybenzoxazole precursor with an oligomer, or by uniform mixing of a polybenzoxazole resin obtained by ring closure of a polybenzoxazole precursor, with an oligomer.
The second material for electrical insulating organic film according to the present invention is obtained by reacting at least one carbox
Eguchi Toshimasa
Enoki Takashi
Hase Yoko
Murayama Mitsumoto
Yamaji Takashi
Foelak Morton
Sumitomo Bakelite Company Limited
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