JP2001237241A - Low dielectric constant film and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low dielectric constant film used as interlayer insulation with low dielectric constant, low hygroscopic characteristic, and high temperature resistance. SOLUTION: Each bead with low dielectric constant is dispersed uniformly in silica-based monomer and polymerized. Alternatively, a thermally decomposing foaming agent is added to an initial polymerized body of polyamide-acid initially. Then, the initial polymerized body is foamed and polymerized, and independent bubbles with diameter of 20 nm or below is dispersed uniformly to form the low dielectric constant film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an interlayer insulating film used for a semiconductor device and a semiconductor device using the same.

[0002]

2. Description of the Related Art In semiconductor devices such as ICs and LSIs, the dielectric constant of an interlayer insulating film of a semiconductor device is increased in order to maintain high electrical performance such as high integration and miniaturization, reduction of wiring delay time and leakage current. Reduction is required.

At present, a silica-based coating widely used as an interlayer insulating film has a relative permittivity of 4 to 4 for a silicon oxide film.
5. The carbon-containing silica film is about 3 to 4 and needs to be further reduced.

Further, since an organic film is more likely to lower the dielectric constant than a silica film, an organic interlayer insulating film such as a fluorine resin or a fluorine-containing polyimide resin has been developed.
However, the organic molecular structure tends to have high hygroscopicity and, consequently, high water permeability, so that copper used for wiring is easily corroded, and heat resistance, mechanical properties and chemical resistance are also high. There are many insufficient points.

[0005] Further, there is a problem that there is no solvent for uniformly dissolving the low dielectric constant organic molecules themselves, so that the solution cannot be uniformly applied. For example, JP-A-7-76644,
JP-A-3-282874 describes low dielectric constant films of a fluorine resin and a fluorine-containing polyimide resin, respectively. However, each has a glass transition temperature of 250 ° C. or lower, and at a temperature higher than the glass transition temperature, the linear expansion coefficient is about 3 to 5 times that of the metal used for the wiring. In view of exposure to high temperatures, the mechanical properties at high temperatures are insufficient.

Japanese Patent Application Laid-Open No. 5-182518 discloses a method of reducing the dielectric constant by dispersing porous microspheres in a film. The effect is small because the difference between
Another problem is that the glass transition temperature of the organic resin is low and the hygroscopicity is high.

On the other hand, porous membranes have been actively developed in recent years.
However, Japanese Patent Application Laid-Open No. H8-5936, which includes gelling and drying steps.
In the method described in Japanese Patent Publication No. 2 (1994), the process is complicated, a porous film having a uniform diameter of 20 nm or less and having an independent particle diameter is difficult to obtain, and cannot be applied to a semiconductor device having a wiring interval of 0.1 μm.

In the method described in Japanese Patent Application Laid-Open No. 11-217458, since the relative dielectric constant is set to 2 or less using alkoxysilane, the porosity is increased and the mechanical properties are reduced. Polishi
ng) is used, but there is a problem that peeling between the wiring and the low dielectric constant film easily occurs.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the dielectric constant of a silica-based low dielectric constant film while maintaining mechanical properties and moisture absorption characteristics, and to provide an organic low dielectric constant film. The purpose is to improve mechanical properties and moisture absorption properties and to lower the dielectric constant.

[0010]

According to the present invention, there is provided a low dielectric constant film comprising a silica-based low dielectric constant film containing beads (microspheres) having a particle diameter of 20 nm or less and a relative dielectric constant of 2.8 or less. In the rate film.

The low dielectric constant film has the formulas [1] to [3]

[0012]

Embedded image Si (OR) ₄ ... [1] R'Si (OR) ₃ ... [2] R ' ₂ Si (OR) ₂ ... [3] (where R is an alkane having 1 to 5 carbon atoms) , R ′ represents any one of alkanes having 1 to 3 carbon atoms, perfluoroalkane, bromine, chlorine and fluorine) in a solution of at least one compound represented by the formula: 20
This is a low dielectric constant film made of a silica-based coating obtained by dispersing organic beads having a diameter of nm or less and then dehydrating and condensing.

As a result, no voids or the like are formed in the film, so that the mechanical properties are good and the hygroscopicity can be kept low. Further, since the organic beads have a low dielectric constant, the dielectric constant of the entire film can be reduced. This method can be performed with little change in the conventional manufacturing process.

In addition, a thermally decomposable molecule as a foaming agent is added to a solution of an initial polymer such as polyamic acid, and the mixture is heated and foamed together with the polymerization, so that closed cells are formed in the heated and closed polyimide film. In the rate film.

Here, if the diameter of the closed cells is 40 nm or more, water molecules in the film collect and become water droplets, and when used as an interlayer insulating layer of a semiconductor device, it is likely to cause corrosion of copper wiring. Further, in a semiconductor device having a wiring interval of 0.1 μm level, the diameter of the closed cells is 20 nm or less for flattening a new surface formed when an insulating film is etched to form wiring holes or grooves. Preferably, the particle size is 10 nm or less.

Further, by selecting a polyimide having a chemical structure having a high glass transition temperature, the mechanical properties at a high temperature can be maintained, and the closed cells having the above-mentioned particle size can be uniformly dispersed, whereby the mechanical properties of the bubbles can be reduced. It is possible to prevent the deterioration and maintain the moisture absorption resistance.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alkoxysilane or halogenated alkoxysilane used in the present invention is at least one selected from the formulas [1] to [3].

Here, R is CH ₃ , C ₂ H ₅ , C ₃ H ₇ ,
CH (CH ₃ ) ₂ , CH ₂ CH _{3 and the} like;
_{l, F, CH 3, C} 2 H 5, C 3 H 7, CH (CH 3) 2, CH 2
CH ₃ , CF ₃ , C ₂ F ₅ , C ₃ F ₇ , CF (CF ₃ ) ₂ , CF ₂
CF _{3 and the} like.

At the time of the condensation reaction by hydrolysis, basic,
Any of the acidic catalysts can be used. Specific examples include ammonia, nitric acid, phosphoric acid, acetic acid, and formic acid. As the solvent, alcohols, ketones, ethers, and esters are used.

After aging the coating solution dissolved in the solvent, beads having a particle size of 20 nm or less are added, and the mixture is sufficiently stirred and dispersed. In order to lower the dielectric constant of the coating film as a final product, the lower the relative dielectric constant of the beads, the better, and it is necessary that the beads have a relative dielectric constant of 2.8 or less.

In the process of manufacturing a semiconductor device,
The glass transition temperature is preferably 350 ° C. or higher, and more preferably 400 ° C. or higher, since the heat treatment becomes close to 300 to 400 ° C.

Examples of the composition of the beads include polystyrene, polyethylene, fluorinated polyimide, and polytetrafluoroethylene, and it is desirable to crosslink these to increase the glass transition temperature. Particularly, fluorinated polyimide and polytetrafluoroethylene are preferable.

These beads are separated from an aqueous phase polymerized by a known method and dried, or commercially available beads are separated using a fine sieve such as a molecular sieve, and separated into beads having a diameter of 20 nm or less. Take out and use.

When a silica-based film is formed on a silicon wafer using these coating solutions, a dipping method in which the coating solution is dipped in the coating solution for about 3 minutes, or a spin coating method in which the coating is performed using a spin coating apparatus. Is used. The number of revolutions of the spin coat is appropriately adjusted according to the target film thickness. When a thin film is to be formed, the immersion method is desirable.

The prepolymer used in the present invention is:
Any substance other than polyimide acid may be used as long as it is a substance that is polymerized by heat or electron beam irradiation. The resulting film has a glass transition point of 350 ° C. or higher, preferably 400 ° C. or higher, has a high intermolecular interaction and a high molecular symmetry for a low dielectric constant, and has a dipole in the molecule. It is necessary to have a structure with low efficiency.

Examples of the polyamic acid prepolymer include structures represented by the following formulas [4] to [8].

[0027]

Embedded image

[0028]

Embedded image

[0029]

Embedded image

A thermally decomposable molecule as a foaming agent is added to a solution in which one or more of these prepolymers are dissolved, and spin-coated on a silicon wafer.

While the film is cured by irradiation with an electron beam or heating, the thermally decomposable molecules are decomposed to form closed cells.
In order to form closed cells uniformly, the viscosity of the initial polymer should not change suddenly in the temperature range where the blowing agent decomposes,
It is necessary to adjust the degree of polymerization of the initial polymer.

As the solvent, a polar solvent such as N-dimethylacetamide, N-methylsulfoxide and N-methylpyrrolidone is used.

The thermally decomposable molecules used in the present invention are desirably those that associate into spherical molecules having a radius of about 3 to 10 nm because fine closed cells can be uniformly formed. If the thermally decomposable molecule is a polymer and has high compatibility with the base resin prepolymer, open cells are likely to be formed. Is desirable.

Examples of the thermally decomposable molecules include C _n F _{2n + 1} COONH ₄ (n = 1 to 8) and C _m as associative molecules.
H _{2m + 1} COONH ₄ (m = 1 to 8), and non-associative molecules include azodicarbonamide, barium azodicarboxylate, azobisisobutyronitrile, N, N′-
Dinitrosopentamethylenetetramine, 4,4-oxybisbenzenesulfonylhydrazide.

Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 20 g of Si (OCH ₃ ) ₄
20 g of (CH ₂ CH ₃ ) Si (OCH ₃ ) ₃ was dissolved in a mixed solution of 50 g of pure water and 65 g of methanol, and 150 g of a 1.5% nitric acid solution obtained by diluting nitric acid with pure water was added for 2 hours. After the addition, the mixture was aged at room temperature for 20 hours.

Into the above-mentioned coating solution for forming a silica film, polytetrafluoroethylene beads having an average particle size of about 5 nm were added.
g, and after sufficiently stirring, the coating solution was applied onto a silicon wafer at a rotation speed of a spinner head device of 1500 rpm. Then, it was calcined in an air at 300 ° C. for 2 hours in the air.

The obtained silica-based film had a thickness of 400 nm by ellipsometry. It was 2.5 when the relative dielectric constant was measured with the impedance analyzer.

After leaving the wafer at room temperature in the air for 3 days, the water content was evaluated using a TDS (Thermal Desorption Spectroscopy) evaluation apparatus. This TDS evaluation apparatus uses Q-ma gas released when a wafer is heated.
It is evaluated by ss. Wafer temperature from room temperature to 350 ° C
Heating for 40 minutes. At this time, the outgassing released from the wafer was evaluated by Q-mass, and as a result, almost no release of water was detected.

Example 2 CF ₃ Si (OCH ₃ ) ₄ 2
0 g and 20 g of (CF ₂ CF ₃ ) ₂ Si (OCH ₃ ) ₃ were dissolved in a mixed solution of 50 g of pure water and 65 g of methanol, and 150 g of a 1.5% nitric acid aqueous solution obtained by diluting nitric acid with pure water was added. 2
After the addition over time, the mixture was aged at room temperature for 20 hours.

8 g of polystyrene beads having an average particle size of about 5 nm was added to the above-mentioned coating solution for forming a silica film, and the mixture was sufficiently stirred.
The coating solution was applied on a silicon wafer at rpm.

The film was fired in the air at 300 ° C. for 2 hours in the air and measured by ellipsometry. As a result, the thickness of the silica-based film was 390 nm. It was 2.5 when the relative dielectric constant was measured with the impedance analyzer. In the same manner as in Example 1, the water content after leaving the wafer was TDS.
As a result, almost no water release was detected.

[Embodiment 3] Equation

[9] diamine 2.4
4 g (0.01 mol) was dissolved in 50 ml of N-methylsulfoxide, and 2.22 g of an acid anhydride of the formula [10] was added thereto.
(0.01 mol), and the mixture was stirred at room temperature for 6 hours to obtain formula [11].
Was synthesized.

[0044]

Embedded image

In addition, C ₃ F ₇ COO is used as a pyrolytic foaming agent.
After adding 0.46 g (0.002 mol) of NH _4, the mixture was stirred at room temperature for 0.5 hour and then aged at room temperature for 30 minutes.

The coating solution was applied on a silicon wafer at a rotation speed of a spinner head device of 1500 rpm. Thereafter, the foaming agent was thermally decomposed while dehydrating and condensing to form a gas while being heated at 300 ° C. for 1 hour to form closed cells.

It is clear from the infrared absorption spectrum that the polyimide of the formula [12] was formed, and it was determined by ellipsometry that the coating of this polyimide was 400
nm.

As a result of analysis by small angle X-ray scattering (SAXS),
The average particle size was 8 nm. The relative dielectric constant measured by an impedance analyzer was 1.9. The glass transition temperature of the above polyimide material measured by a differential operation calorimeter was 390 ° C. Further, as in Example 1, as a result of evaluating the water content after leaving the wafer by TDS, almost no water release was detected.

Example 4 Diamine of Formula [13]
58 g (0.01 mol) was dissolved in 50 ml of N-methylsulfoxide, and 2.18 of the acid anhydride of the formula [14] was added thereto.
g (0.01 mol), and the mixture was stirred at room temperature for 6 hours.
5] was synthesized.

[0050]

Embedded image

[0051] C ₃ H ₇ COO thereto as thermally decomposable foaming agent
0.21 g (0.002 mol) of NH ₄ was added, and the mixture was stirred and aged in the same manner as in Example 3, and then spin-coated on a silicon wafer.
Heat treatment was performed to form a film.

It was clear from the infrared absorption spectrum that a polyimide of the formula [16] was formed, and the thickness of the polyimide film measured by ellipsometry was 420 nm.

The average particle diameter, relative dielectric constant, and glass transition temperature were measured in the same manner as in Example 3.
1.8, 400 ° C. Further, similarly to the first embodiment,
As a result of evaluating the water content after leaving the wafer by TDS, almost no water release was detected.

Example 5 Diamine of Formula [17] 3.
28 g (0.01 mol) was dissolved in 50 ml of N-dimethylacetamide, and 2.70 of the acid anhydride of the formula [18] was added thereto.
g (0.01 mol), and the mixture was stirred at room temperature for 6 hours.
9] was synthesized.

[0055]

Embedded image

C ₂ F ₅ COO was used as a pyrolytic foaming agent.
0.36 g (0.002 mol) of NH ₄ was added, stirred and aged in the same manner as in Example 3, and then spin-coated on a silicon wafer and heat-treated to form a film.

It is clear from the infrared absorption spectrum that the polyimide of the formula [20] was formed. As a result of measurement by ellipsometry, this polyimide coating was 4%.
30 nm. The average particle diameter, relative dielectric constant, and glass transition temperature were measured in the same manner as in Example 3, and each was 7.2.
nm, 1.8, 390 ° C. In addition, as in Example 1, the water content after the wafer was left was evaluated by TDS.
Almost no water release was detected.

Example 6 Diamine of the formula [21] 2.
34 g (0.01 mol) was dissolved in 50 ml of N-dimethylacetamide, and 2.68 of the acid anhydride of the formula [22] was added thereto.
g (0.01 mol) was added, and the mixture was stirred at room temperature for 6 hours to synthesize a polyamic acid of the formula [23].

[0059]

Embedded image

C ₄ F ₉ COO was used as a pyrolytic foaming agent.
0.56 g (0.002 mol) of NH ₄ was added, stirred and aged in the same manner as in Example 3, and then spin-coated on a silicon wafer and heat-treated to form a film.

It is clear from the infrared absorption spectrum that the polyimide of the formula [24] was formed, and the film of this polyimide measured by ellipsometry was 410 n
m. When the average particle diameter, the relative dielectric constant, and the glass transition temperature were measured in the same manner as in Example 3, each was 7.8 nm,
1.8, 410 ° C. Further, similarly to the first embodiment,
As a result of evaluating the water content after leaving the wafer by TDS, almost no water release was detected.

Example 7 Diamine of Formula [25] 1.
72 g (0.01 mol) was dissolved in 50 ml of N-dimethylacetamide, and 2.57 of the acid anhydride of the formula [26] was added thereto.
g (0.01 mol) was added and the mixture was stirred at room temperature for 6 hours to synthesize a polyamic acid of the formula [27].

[0063]

Embedded image

C ₄ F ₉ COO was used as a pyrolytic foaming agent.
0.56 g (0.002 mol) of NH ₄ was added, and the mixture was stirred and aged as in Example 3, spin-coated on a silicon wafer, and heat-treated to form a film.

From the infrared absorption spectrum, it is clear that the polyimide of the formula [28] was formed, and the film of this polyimide measured by ellipsometry was 420 nm.
m.

The average particle diameter, relative dielectric constant, and glass transition temperature were measured in the same manner as in Example 3.
1.9, 390 ° C. Further, similarly to the first embodiment,
As a result of evaluating the water content after leaving the wafer by TDS, almost no water release was detected.

Example 8 Using the low dielectric constant film of Example 1, the wiring delay time of a semiconductor device having an interlayer insulating film 6 formed thereon as shown in FIG. 1 was measured. The wiring delay time could be reduced to 88% as compared with the semiconductor device using the low dielectric constant film of Comparative Example 1 described later.

Example 9 Using the low dielectric constant film of Example 3, the wiring delay time of a semiconductor device having an interlayer insulating film 6 formed thereon as shown in FIG. 1 was measured. The wiring delay time was reduced to 78% as compared with the semiconductor device using the low dielectric constant film of Comparative Example 3 described later.

Further, by using the low dielectric constant films of Examples 8 and 9 as the interlayer insulating film of the semiconductor device, the wiring delay time can be reduced.

Comparative Example 1 20 g of Si (OCH ₃ ) ₄
20 g of (CH ₃ CH ₃ ) Si (OCH ₃ ) ₃ was dissolved in a mixed solution of 50 g of pure water and 65 g of methanol, and 150 g of a 1.5% nitric acid aqueous solution obtained by diluting nitric acid with pure water was added for 2 hours. After the addition, the mixture was aged at room temperature for 20 hours. The coating solution was applied onto a silicon wafer at a rotation speed of a spinner head device of 1500 rpm.

Thereafter, the mixture was fired in an autoclave at 300 ° C. for one hour in the air. The silica-based coating measured by ellipsometry was 400 nm. It was 2.9 when the relative permittivity was measured with the impedance analyzer.

[Comparative Example 2] 2 of CF ₃ Si (OCH ₃ ) ₄
0 g and (CF ₂ CF ₃ ) ₂ Si (OCH ₃ ) ₃ in 20 g of pure water.
0 g and 65 g of methanol were dissolved in a mixed solution, and nitric acid was diluted with pure water.
g was added over 2 hours and aged at room temperature for 20 hours.

The number of revolutions of the spinner head device is set to 1500
The coating solution was applied on a silicon wafer at rpm. Then, it was fired in an air at 300 ° C. for 1 hour in the air. This silica-based coating measured by ellipsometry was 4
00 nm. It was 2.8 when the relative dielectric constant was measured with the impedance analyzer.

[Comparative Example 3] The same as in Example 3,

[9]
Is dissolved in 50 ml of N-methylsulfoxide, 2.22 g (0.01 mol) of the acid anhydride of the formula [10] is added thereto, and the mixture is added at room temperature for 6 hours. With stirring, the polyamic acid of the formula [11] was synthesized.

In the same manner as in Example 3, a film was formed by spin-coating a silicon wafer and then performing a heat treatment.

It is clear from the infrared absorption spectrum that the polyimide of the formula [12] was formed, and the film of this polyimide measured by ellipsometry was 240 nm.
m. The relative dielectric constant measured with an impedance analyzer was 2.6.

[Comparative Example 4] As in Example 4, the formula [1]
2.5 g (0.01 mol) of the diamine of 3) was added to 50 ml of N
-Methyl sulfoxide, 2.18 g (0.01 mol) of the acid anhydride of the formula [14] was added thereto, and the mixture was stirred at room temperature for 6 hours to synthesize a polyamic acid of the formula [15].

In the same manner as in Example 4, a silicon wafer was spin-coated and then heat-treated to form a film.

It is clear from the infrared absorption spectrum that the polyimide of the formula [16] was formed, and the film of this polyimide measured by ellipsometry was 250 nm.
m. The relative dielectric constant and the glass transition temperature were measured in the same manner as in Example 4. As a result, they were 2.5 and 400 ° C., respectively.

[Comparative Example 5] As in Example 5, the formula [1]
7] with 3.28 g (0.01 mol) of diamine in 50 ml of N
Was dissolved in dimethylacetamide, and 2.70 g (0.01 mol) of the acid anhydride of the formula [18] was added thereto, followed by stirring at room temperature for 6 hours to synthesize a polyamic acid of the formula [19].

In the same manner as in Example 5, a film was formed by spin-coating on a silicon wafer, followed by heat treatment. From the infrared absorption spectrum, it is clear that the polyimide of the formula [20] is formed, and the polyimide film has a thickness of 260 nm.
Met. The relative dielectric constant and the glass transition temperature were measured in the same manner as in Example 5, and were 2.6 and 400 ° C., respectively.

[Comparative Example 6] In the same manner as in Example 6, the formula [2]
2.31 g (0.01 mol) of the diamine of 1) was added to 50 ml of N
-Dissolved in dimethylacetamide, 2.68 g (0.01 mol) of the acid anhydride of the formula [22] was added thereto, and the mixture was stirred at room temperature for 6 hours to synthesize a polyamic acid of the formula [23].

As in Example 6, a film was formed by spin-coating on a silicon wafer and heat-treating. It is clear from the infrared absorption spectrum that the polyimide of the formula [24] was formed, and the coating of this polyimide was 250 n
m. The relative dielectric constant and glass transition temperature were measured in the same manner as in Example 7, and were 2.6 and 420 ° C., respectively.

[Comparative Example 7] In the same manner as in Example 7, the formula [2]
5] 1.72 g (0.01 mol) of diamine was added to 50 ml of N
Was dissolved in dimethylacetamide, and 2.57 g (0.01 mol) of the acid anhydride of the formula [26] was added thereto, followed by stirring at room temperature for 6 hours to synthesize a polyamic acid of the formula [27].

After the spin coating in the same manner as in Example 7, a heat treatment was performed to form a film. From the infrared absorption spectrum, the formula [2
It was clear that the polyimide of No. 8] was formed, and the thickness of the polyimide film measured by ellipsometry was 250 nm. The relative permittivity and the glass transition temperature were measured in the same manner as in Example 7, and the values were 2.9 and 39, respectively.
It was 0 ° C. As in Example 7, as a result of evaluating the water content after leaving the wafer by TDS, almost no water release was detected.

[Comparative Example 8] In the same manner as in Example 7, the formula [2]
5] 1.72 g (0.01 mol) of diamine was added to 50 ml of N
Was dissolved in dimethylacetamide, and 2.57 g (0.01 mol) of the acid anhydride of the formula [26] was added thereto, followed by stirring at room temperature for 6 hours to synthesize a polyamic acid of the formula [27].

As a thermal decomposition type foaming agent, a polymerization degree of 100
Was spin-coated in the same manner as in Example 7, followed by heat treatment to form a film. From the infrared absorption spectrum, it was clear that a polyimide represented by the formula [28] was formed, and the thickness of the polyimide film measured by ellipsometry was 430 nm. The relative dielectric constant and the glass transition temperature were measured in the same manner as in Example 7, and were 1.8 and 390 ° C., respectively.

When the average pore size was measured in the same manner as in Example 7, it was 40 nm, but the variation in the pore size was larger than in Example 7. As in Example 7, as a result of evaluating the water content after leaving the wafer by TDS, one or more orders of magnitude more water were detected than in Example 7.

[Comparative Example 9] [Comparative Example 9]
5] 1.72 g (0.01 mol) of diamine was added to 50 ml of N
Was dissolved in dimethylacetamide, and 2.57 g (0.01 mol) of the acid anhydride of the formula [26] was added thereto, followed by stirring at room temperature for 6 hours to synthesize a polyamic acid of the formula [27].

To this, 1 g of azodicarbonamide was added as a pyrolysis type foaming agent, and spin-coated as in Example 7, followed by heat treatment to form a film. From the infrared absorption spectrum, it was clear that the polyimide represented by the formula [28] was formed, and the thickness of the polyimide film measured by ellipsometry was 420 nm. The relative permittivity and the glass transition temperature were measured in the same manner as in Example 7.
9, 400 ° C. When the average pore size was measured in the same manner as in Example 7, it was 12 nm, but the variation in the pore size was larger than in Example 7.

As in the case of Example 7, the water content after the wafer was left was evaluated by TDS, and as a result, water several times that of Example 7 was detected.

As can be seen from a comparison between Examples 1 and 2 and Comparative Examples 1 and 2, the addition of beads having a low dielectric constant can lower the dielectric constant and suppress the hygroscopicity.

Further, as can be seen from a comparison between Examples 3 to 7 and Comparative Examples 3 to 7, by adding thermally decomposable molecules and foaming, uniform closed cells are formed and the dielectric constant is lowered. And moisture absorption can be suppressed to a low level.

Further, by comparing Example 7 with Comparative Examples 8 and 9, the thermally decomposable molecule is most preferably an associative molecule in terms of the pore diameter of the closed cell and its variation (Comparative Example 8). It can be seen that, if it is a polymer, the pore size increases and the cells become open cells, increasing the hygroscopicity (Comparative Example 9).

[0095]

The silica-based low dielectric constant film of the present invention can lower the dielectric constant by adding a low dielectric constant bead without changing the manufacturing process of the conventional silica-based low dielectric constant film. The wiring delay time can be reduced.

Further, since the organic low dielectric constant film of the present invention has closed cells having a uniform pore size, the dielectric constant can be made lower than that of the conventional organic low dielectric constant film, and the wiring delay time can be reduced. Shortening can be achieved.

In addition, since the polyamic acid prepolymer having a high glass transition temperature is used, the durability against the temperature is large, and the heat treatment in the manufacturing process can be sufficiently endured.
Reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a semiconductor device using a low dielectric constant film of the present invention.

[Explanation of symbols]

1 ... p-type Si, 2 ... n-type Si, 3 ... gate electrode, 4 ... S
i board, 5 ... SiO _2, 6 ... interlayer insulating film, 7 ... W, 8 ...
Al, 9 ... Cu, 10 ... SiN.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 25/06 C08L 25/06 27/18 27/18 83/00 83/00 H01L 21/316 H01L 21 / 316 G 21/768 C08L 79:08 // C08L 79:08 H01L 21/90 SF term (reference) 4F074 AA74 BA13 BA14 BA15 BA16 BA18 BA19 BA20 CA29 DA03 DA12 DA59 4J002 BB03X BC03X BD15X CM04X CP02W CP03W CP08W FA02X 4J04 QB15 QB26 RA06 RA35 SA06 SB01 TA22 TB01 UA121 UA122 UA131 UA132 UA262 UA332 UB051 UB061 UB402 YA06 ZA43 ZA46 ZB50 5F033 HH08 HH11 JJ19 KK01 BK08 RR09 RR22 RR23 SS22 A01 AC02 A01 AC04 A02 ACOA BJ01 BJ02

Claims (7)

[Claims] 1. A low dielectric constant film comprising a silica-based low dielectric constant film containing beads (microspheres) having a particle diameter of 20 nm or less and a relative dielectric constant of 2.8 or less. 2. The low dielectric constant film according to claim 1, wherein the beads are at least one of polyethylene, polystyrene, fluorinated polyimide, and polytetrafluoroethylene. 3. The silica-based low dielectric constant film according to the formula [1]
[3] embedded image Si (OR) ₄ ... [1] R′Si (OR) ₃ ... [2] R ′ ₂ Si (OR) ₂ ... 5. The alkane of formula (5) and R 'represent one or more of alkanes having 1 to 3 carbon atoms, perfluoroalkane, bromine, chlorine and fluorine). 4. The low dielectric constant film according to 1. 4. A closed cell having a particle size of 20 nm or less is formed in a polyimide film which is heated and closed by adding a thermally decomposable foaming agent to a solution of the polyamic acid polymer, heating and polymerizing the thermally decomposable foaming agent together with polymerization. A low dielectric constant film having a glass transition temperature of 350 ° C. or higher. 5. The low dielectric constant film according to claim 4, wherein the thermally decomposable blowing agent is a molecule associated in a solution of a polyimide acid polymer, and the closed cells have a particle diameter of 20 nm or less and are uniformly dispersed. . 6. The low dielectric constant film according to claim 5, wherein the closed cells have a particle size of 10 nm or less. 7. A semiconductor device provided with an interlayer insulating film, wherein the interlayer insulating film is formed of the low dielectric constant film according to claim 1.