JPH11263916A - Low dielectric constant insulating material for wiring circuit and electronic parts using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low dielectric constant insulating material for wiring circuit of fine patterns by including an insulating resin base and compounds which us obtained from chemical modification of a fullerence or a carbon nano- tube. SOLUTION: This material comprises (A) an insulating resin base (polyimide, silicone resin and the like) and (B) the compounds obtained by chemically modifying the fullerene (hollow spheroidal molecular compounds having carbon network structure on the surface) or the carbon nano-tube (hollow cylindrical molecular compounds having carbon network structure on the surface), with compounds including silicone based functional groups, or substituents including oxygen [-Si(CH3 )3 or -Si(CH3 )2 OCH3 or the like]. For forming space contributing to the reduction of the dielectric constant of the insulating material, the fullerenes or the like, preferably have angstrom or more of carbon-carbon distance of the molecular longitudinal axis of the fullerenes (C20 or C30 fullerene or the like).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlayer insulating material for a low dielectric constant multilayer circuit wiring suitable for high-speed propagation of signals by mounting electronic devices such as semiconductor elements at high density, and such a multilayer circuit wiring board. And electronic components such as large-scale integrated circuits (LSI).

2. Description of the Related Art The speed of semiconductor devices used in various computers ranging from personal computers to high-performance computers has been remarkably increased, and the transmission delay in a wiring section of a board relatively affects the operation speed of the computer. . As a result, resin thin film wiring suitable for high-density and fine multi-layer wiring using a resin thin film as an interlayer insulating film has come to be applied to a circuit board for a central processing unit (CPU) of a computer. In order to realize a higher-speed computer in the future, it is essential to develop a low-dielectric-constant insulating material that utilizes high-density and fine multilayer wiring and is suitable for high-speed signal propagation.

[0003]

2. Description of the Related Art Conventionally, resins such as epoxy and polyimide have been used as high-density mounting board materials used in high-speed computers. Furthermore, recently, olefin-based and fluorine-based materials have been attracting attention as resins having lower dielectric constants.

The relative permittivity ε _s of a material is expressed as follows according to the Clausius-Mossottey equation.

[0005]

(Equation 1)

Where α in this equation is the polarizability of the material molecule,
N is the number of molecules per unit volume, and ε ₀ is the dielectric constant in vacuum.

As can be seen from the above equation, solving for ε _{s and} performing partial differentiation with α or N, the relative permittivity ε _s decreases as the polarizability α decreases and the number of molecules N per unit volume decreases. Become. This relationship is expressed by Nα and the relative dielectric constant ε shown in FIG.
_This is clear from a graph showing an example of the relationship with _s . Hereinafter, the relative dielectric constant is simply referred to as “dielectric constant”.

As described above, the use of an olefin-based or fluorine-based resin is effective in suppressing the material's polarizability α. However, it is known that their dielectric constants do not fall below 2. In addition, these resin materials,
At present, there are still many things to be solved, such as self-fusing properties, adhesion to conductive metals, and workability of via holes between layers.

On the other hand, there is a method of lowering the dielectric constant by reducing the number N of molecules per unit volume. For example, there are foamed materials having a small number of molecules per unit volume, but it is clear that these are not suitable as insulators having a thickness of the order of several μm or tens of μm of fine wiring.

In order to reduce the weight of the insulating film and to reduce the coefficient of thermal expansion, it is conceivable to mix glass fibers or carbon fibers into a resin material to form a composite. However, glass fibers have the disadvantage of increasing the dielectric constant. In addition, carbon fibers have a drawback of lowering the dielectric strength.

Further, in order to reduce the dielectric constant of the material by introducing a space at the molecular level, a method of mixing fullerene or the like having a structure with a space in the molecule with a resin material can be considered, but fullerene is limited. There is a problem that only a very small amount is dissolved in the obtained solvent, so that even when mixed with the resin, the phase is easily separated.

[0012]

The dielectric constant of an olefin-based or fluorine-based resin material, which is attracting attention as an interlayer insulating film material having a body dielectric constant in the future, is in the range of about 2.1 to 2.8. Until now, some materials have been proposed that have a dielectric constant lower than these materials, but they have characteristics that can be used in actual manufacturing or mounting processes, and have self-fusing properties and adhesion to conductive metals. , Via hole processability between layers, etc.
There is still great expectation for a practical low dielectric constant interlayer insulating material having essential properties as an insulating material.

An object of the present invention is to provide a new material useful as a low dielectric constant insulating material for fine pattern circuit wiring in response thereto. It is another object of the present invention to provide an electronic component including an insulating film formed from such a new low dielectric constant insulating material.

[0014]

The insulating material for circuit wiring of the present invention is characterized by containing an insulating resin base and a compound obtained by chemically modifying fullerene or carbon nanotube.

As described above, the present invention is to improve the compatibility with a resin by chemically modifying fullerenes and carbon nanotubes, which have essentially poor compatibility with a resin used as a base material for an insulating film. By increasing the amount of dispersion of fullerenes and carbon nanotubes in the resin,
This achieves a low dielectric constant of the formed insulating film.

[0016] Fullerenes and carbon nanotubes are well known as substances having a structure having a space in a molecule composed of only carbon atoms. Fullerene is a compound of a hollow spherical molecule having a network structure formed of carbon atoms on the surface, and a carbon nanotube is a compound of a hollow cylindrical molecule having a network structure formed of carbon atoms on the surface. is there. These may be synthesized or commercially available ones may be used.

Fullerenes and the like can be chemically modified by using, for example, organolithium or Grignard reagents (Nagashima, Kamino, Ito, Journal of the Chemical Society of Japan, Vo
l. 2, p91 (1997)). Thereby, the compatibility between the fullerene and the like and the insulating resin such as the polyimide is improved, and the space in the resin is enlarged, so that the dielectric constant of the formed insulating film can be reduced. Alternatively, fullerene or the like can be given reactivity with an insulating resin by chemical modification.

Chemical modification of fullerenes or carbon nanotubes can be performed, for example, with a silicone-based functional group or a substituent containing oxygen. Examples of substituents containing a silicone-based functional groups and _{oxygen, -Si (CH 3) 3,} -Si
(CH ₃ ) ₂ OCH ₃ , —Si (CH ₃ ) (OCH ₃ )
₂ , -Si (CH ₃ ) (OCH (CH ₃ ) ₂ ) _{2 and the} like. Fullerenes or carbon nanotubes chemically modified with these improve the compatibility with the base resin of the insulating material. A functional group having an unsaturated bond may be added to increase the reactivity of fullerene or carbon nanotube. Representative examples of the functional group having an unsaturated bond include an allyl group, an aryl group, and -C≡CR (R is an alkyl group).
Further, adding hydrogen or fluorine to fullerene or carbon nanotube molecules to make a part of a conjugated system of these molecules into a saturated bond is also effective for lowering the dielectric constant of the insulating material.

The space that contributes to the decrease in the dielectric constant of the insulating material is
In order to form, carbon in the molecular long axis direction such as fullerene
The distance between carbons is at least 4 Å (0.
4 nm) or more. As an example, the molecular long axis
The carbon-to-carbon distance in the direction is 4 angstroms (0.
4 nm) or more as fullerene,₂₀, C_{twenty four},
C ₂₆, C₂₈, C₃₀, C₃₂, C₃₆, C₅₀, C₆₀, C₇₀, C
₇₆, C₇₈, C₈₀, C₁₈₀, C₂₄₀, C₃₂₀, C₅₄₀Such
Can be considered.

The insulating material of the present invention can be prepared by mixing chemically modified fullerene or carbon nanotube with a base resin of the insulating material. If necessary, a solvent may be used. Fullerene or carbon nanotubes can be added to the base resin or the base resin solution until saturation, although it depends on the solubility in the base resin or base resin solution. In the case where the maximum addition amount is used, for example, when the heat resistance of the formed insulating film becomes a problem, the addition amount of fullerene or the like should be reduced. In any case, the amount of fullerenes or carbon nanotubes mixed in the insulating material of the present invention can be easily determined by experiment according to the type of the base resin and the characteristics required for the insulating film.

The base resin may be any of low-permittivity resins used for manufacturing multilayer wiring. If the base resin is a polyimide or silicone resin, these are particularly excellent in heat resistance, which is advantageous in terms of the assembly process of electronic components and the reliability of products.

In order to form an interlayer insulating film of a multilayer circuit board from the insulating material of the present invention, the insulating material is applied to the substrate, dried, and then the base resin is cured. It is not well-known here.

The insulating film formed from the insulating material of the present invention comprises:
It has low dielectric constant, low thermal expansion, and high insulating properties due to the effect of the carbon compound having a space at the molecular level dispersed in the base resin. An electronic component such as an LSI using this insulating film as an interlayer insulating film, for example, can have a high-density and fine multilayer wiring structure, and greatly contributes to improvement in the operation speed of various computers.

[0024]

Next, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to these embodiments.

[0025] After dissolving Example 1 C ₆₀ fullerene (manufactured by Aldrich) until supersaturation 70g of tetrahydrofuran (THF), a Grignard reagent ClMgCH
_{Using 2} SiMe ₂ (OCH (Me) ₂ ) (Me in this formula represents a methyl group), an addition reaction was performed at a temperature of 20 ° C. for 2 hours. After the addition reaction, the THF was removed of the solvent, the C ₆₀ fullerenes this chemical modification, JP-8-2
No. 59784, 6-methyl-1,
4,5,8-Dimethano-1,2,3,4,4a, 5
Ring opening polymerization of 8,8a-octahydronaphthalene by a known method and hydrogenation of alicyclic polyolefin 10
In addition to weight% THF solution, made an insulating material solution saturated with chemically modified C ₆₀ fullerene.

Next, this solution was spin-coated on a silicon substrate, dried, and thermally cured at 220 ° C. for 5 minutes. Furthermore, as an after cure, an oxygen concentration of 10 ppm
Thermal curing was performed at 200 ° C. for 5 hours in the following nitrogen atmosphere to form an insulating film. The dielectric constant of this insulating film was measured at 1 MHz by depositing a gold electrode (1 mm × 1 mm).
2.2.

[0027] After dissolving Example 2 C ₆₀ fullerene (manufactured by Aldrich) until supersaturation 70g of tetrahydrofuran (THF), a Grignard reagent ClMgCH
_{Using 2} SiMe ₂ (OCH (Me) ₂ ) (Me in this formula represents a methyl group), an addition reaction was performed at a temperature of 20 ° C. for 2 hours. This product was further subjected to an addition reaction (20 ° C., 2 hours) with t-butyllithium to obtain C ₆₀
Fullerene was added with hydrogen and a t-butyl group. After completion of the reaction, the THF was removed of the solvent, in addition to 10 wt% THF solution of the same alicyclic polyolefin as that used for C ₆₀ fullerenes This chemical modification in Example 1, in chemically modified C ₆₀ fullerene A saturated insulating material solution was made.

Next, this solution was applied on a silicon substrate, dried, and thermally cured at 220 ° C. for 5 minutes. Further, as an after cure, thermal curing was performed at 200 ° C. for 5 hours in a nitrogen atmosphere having an oxygen concentration of 10 ppm or less to form an insulating film. When the dielectric constant of this insulating film was measured as described in Example 1, the dielectric constant was 2.0.

[0029] dissolving the same C ₆₀ fullerene as used in COMPARATIVE EXAMPLE Example 1, until again saturates 10 wt% THF solution of the same alicyclic polyolefin as used in Examples 1 and 2 I let it. The solution of the insulating material thus prepared was applied on a substrate, dried, and thermally cured at 220 ° C. for 5 minutes. Further, as an after cure, thermal curing was performed at 200 ° C. for 5 hours in a nitrogen atmosphere having an oxygen concentration of 10 ppm or less to form an insulating film. The dielectric constant of this insulating film measured by the method described in Example 1 was 2.8.

[0030]

As described above, according to the present invention,
Fullerenes and carbon nanotubes that can form a space at the molecular level can be effectively incorporated into an insulating material, so that an insulating film with a low dielectric constant that can be applied to a fine pattern can be provided. It is possible to provide an electronic component including a multilayer circuit board suitable for propagation.

[Brief description of the drawings]

[1] and the product of the number of molecules N and polarizability in a unit volume of material alpha, is a graph showing the relationship between the relative dielectric constant epsilon _s.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/768 H01L 21/90 S (72) Inventor Hiroyuki Sato 4-1-1 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Stock Inside the company (72) Inventor Takao Yokouchi 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Shunichi Fukuyama 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Inside (72) Inventor Yoshihiro Nakata 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (6)

[Claims] 1. An insulating material for circuit wiring, comprising an insulating resin base and a compound obtained by chemically modifying fullerene or carbon nanotube. 2. The insulating material for circuit wiring according to claim 1, wherein the fullerene or carbon nanotube has a carbon-carbon distance of 4 angstroms (0.4 nm) or more. 3. The insulating material for circuit wiring according to claim 1, wherein the chemical modification is made of a silicone-based functional group, a substituent containing oxygen, a substituent having an unsaturated bond, or a fluorine atom. 4. The insulating material for circuit wiring according to claim 1, wherein the insulating resin base is a polyimide or a silicone resin. 5. An insulating film for circuit wiring, which is formed by curing the material according to claim 1. 6. An electronic component including a multilayer circuit wiring board using the insulating film according to claim 5.