JP2000100808A - Insulating film forming material and semiconductor device including insulating film formed from the material - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To realize a high-speed device by maximizing the effect of reducing the parasitic capacitance by reducing the dielectric constant, furthermore, it is superior in heat resistance and moisture resistance and suppresses copper diffusion. Provided is a material for forming a dielectric constant insulating film, and a high-speed and highly reliable semiconductor device including the insulating film formed from the material. SOLUTION: The insulating film forming material of the present invention is composed of an arylene ether-based polymer having an adamantane ring in a main chain skeleton, and a solvent solution thereof is applied to a substrate and subjected to a heat treatment to form an insulating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an insulating film for a semiconductor integrated circuit. More specifically, the present invention relates to an insulating film having a low dielectric constant and excellent heat resistance and moisture resistance, which is useful in highly integrated semiconductor devices such as ICs and LSIs, and a high-speed insulating film using the insulating film. And a highly reliable semiconductor device.

[0002]

2. Description of the Related Art With an increase in the degree of integration of semiconductor integrated circuits and an increase in element density, a demand for multi-layer semiconductor elements has been increasing. In a multilayer wiring of a semiconductor integrated circuit, a reduction in signal propagation speed is determined by a wiring resistance and a parasitic capacitance between wirings. As the integration density increases, the spacing between wirings becomes narrower, and wiring delay due to an increase in capacitance (parasitic capacitance) between wirings has become a problem.

As described above, the wiring delay (T) is affected by the wiring resistance (R) and the capacitance (C) between the wirings, and is expressed by the following equation (1). T∝CR (1) In Expression (1), if C is expressed as a relationship with ε _r (dielectric constant), Expression (2) is obtained. C = ε ₀ ε _r S / d (2) In this equation, S represents an electrode area, ε ₀ represents a dielectric constant of vacuum, and d represents a wiring interval.

[0004] The capacity of the insulating film can be reduced by reducing the wiring thickness and the cross-sectional area, but if the wiring thickness is reduced, the wiring resistance is further increased.
In order to increase the speed, it is essential to reduce the resistance of the wiring and the dielectric constant of the insulating film, and these are expected to be major factors that govern the performance of the semiconductor device. That is, to reduce the wiring delay, it is effective to reduce the dielectric constant of the insulating film.

Conventionally, as an insulating material in a semiconductor device, an inorganic material such as silicon dioxide (SiO ₂ ), silicon nitride (SiN), or phosphosilicate glass (PSG), or an organic polymer material such as polyimide or Teflon is used. Has been used. However, the dielectric constant of a SiO ₂ film formed by chemical vapor deposition (CVD-SiO ₂ film) most used in a semiconductor device is about 4. Further, the SiOF film studied as a low dielectric constant CVD film has a dielectric constant of about 3.3 to 3.5, but has a high hygroscopic property, and has a problem that the dielectric constant increases due to moisture absorption over time. is there. In recent years, copper wiring has been studied to reduce wiring resistance.
In a SiO ₂ -based insulating film containing H, copper is easily diffused by heat treatment at 200 ° C. in a state of being in contact with copper. Are known.

On the other hand, it is known that copper diffusion does not occur in an organic polymer film having a low dielectric constant of 2.5 to 3.0. However, the polyimide organic polymer material has a low glass transition temperature of 200 to 350 ° C. and a large coefficient of thermal expansion, and thus has a problem of damage to wiring. Also,
Teflon-based materials have poor adhesion to other materials, and tend to form voids beside wiring. This wiring side void causes a short circuit between wiring layers when a positional shift occurs at the time of opening a via hole for forming a multilayer wiring. Therefore, at present, sufficient characteristics cannot be obtained from the viewpoint of forming a low resistance wiring and a low dielectric constant insulating layer which are indispensable for realizing a high speed device.

[0007]

Conventionally, it has been known that the signal propagation speed is reduced due to the parasitic capacitance of the insulating film. However, in the generation in which the wiring interval of the semiconductor device is 1 μm or more, the effect of the wiring delay on the entire device is not considered. There were few. However, when the wiring interval is less than 1 μm, the influence on the device speed becomes large,
In particular, when a circuit is formed with a wiring interval of 0.5 μm or less in the future, the parasitic capacitance between the wirings will greatly affect the device speed.

An object of the present invention is to make it possible to realize a high-speed device by making the most of the effect of reducing the parasitic capacitance by lowering the dielectric constant, and to further excel in heat resistance and moisture resistance and suppress copper diffusion. And a material for forming the low dielectric constant insulating film. It is also an object of the present invention to provide a high-speed and highly reliable semiconductor device including an insulating film formed from such an insulating film forming material.

[0009]

The insulating film forming material of the present invention is an arylene ether polymer having an adamantane ring in a main chain skeleton.

A semiconductor device according to the present invention is a semiconductor device including a substrate and a plurality of insulating layers and a plurality of wiring layers alternately formed thereon, wherein at least one of the insulating layers mainly includes It is characterized by being formed from an insulating film forming material of an arylene ether-based polymer having an adamantane ring in a chain skeleton.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polymer of the insulating film forming material of the present invention is an arylene ether polymer having an adamantane ring in the main chain skeleton, that is, a polymer having both an adamantane ring and a benzene ring in the main chain skeleton. It is. This polymer can be represented, for example, by the following general formula (1).

[0012]

Embedded image

In this formula, each R ^A is independently hydrogen,
A monovalent hydrocarbon group or a phenyl group having 1 to 3 carbon atoms, and R ¹ and R ² may be the same or different;

[0014]

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Wherein each R ³ is independently hydrogen or a monovalent hydrocarbon group having 1 to 3 carbon atoms;
n is an integer such that the weight average molecular weight of the polymer is 500 to 50,000.

In another embodiment, the polymer of the insulating film forming material of the present invention can be represented by the following general formula (2).

[0017]

Embedded image In this formula, each ^RA is independently hydrogen, carbon number 1-3.
A monovalent hydrocarbon group or a phenyl group, R ⁵ and R
⁶ may be the same or different and are represented by -O- or

[0018]

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Wherein R ⁸ is -O
-Or

[0020]

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Wherein R ⁹ is hydrogen or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and p and q are such that the weight average molecular weight of the polymer is 500 to 50,000. And p: q = 1: 0.2 to 1: 2.

Examples of the hydrocarbon group of R ³ and R ⁹ are a methyl group, an ethyl group, a propyl group, a vinyl group and an allyl group.

As described above, the polymer of the insulating film forming material according to the present invention is characterized in that an adamantane ring in addition to a benzene ring is contained in the main chain skeleton. The adamantane ring is thermally stable and, because of its fused ring structure, can reduce the film density without lowering the heat resistance. One or more monovalent hydrocarbon groups having 1 to 3 carbon atoms (eg, methyl group, ethyl group, propyl group) or phenyl groups may be bonded to the adamantane ring as a substituent other than hydrogen. Further, since this polymer has a low polarity, it does not have hygroscopicity, which causes the dielectric constant to increase with time as seen in the SiOF film. Therefore, the polymer of the present invention is an insulating film forming material having both heat resistance, moisture resistance and low dielectric constant, and the insulating film formed of the material of the present invention has a dielectric constant of 3 or less. Therefore, the insulating film according to the present invention is effective as a low dielectric constant interlayer insulating film of a semiconductor device, and a semiconductor device having a high response speed can be obtained by using this insulating film.

The weight average molecular weight of the arylene ether polymer containing an adamantane ring of the insulating film forming material of the present invention is preferably in the range of 500 to 50,000. When the weight average molecular weight is 500 or less, the polymer evaporates by heat treatment at 300 ° C. or more, and when the weight average molecular weight is 50,000 or more, the solubility of the polymer in a coating solvent for forming an insulating film decreases.

The polymer of the insulating film forming material of the present invention can be easily prepared from the corresponding monomer by using a method usually used in organic synthesis. For example, a desired polymer can be obtained by reacting monomers using a catalyst in a solvent.

When an insulating film is formed using the insulating film forming material of the present invention, a solution obtained by dissolving a polymer of the insulating film forming material in an appropriate coating solvent is generally used. The coating solvent is not particularly limited as long as the polymer of the present invention dissolves. Examples of such a coating solvent include toluene, xylene, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, cyclopentanone and the like.

The insulating film using the insulating film forming material of the present invention is formed by applying a solution obtained by dissolving a polymer in a coating solvent on a substrate by a spin coating method and performing a heat treatment at 120 to 350 ° C. After drying the solvent for about 10 minutes)
Heat treatment (for example, 30 minutes or more) at 350 to 450 ° C. in an inert atmosphere (for example, in an inert gas having an oxygen concentration of 100 ppm or less) can be performed.
If the solvent drying temperature is lower than 120 ° C., the solvent drying is insufficient, and if the solvent drying temperature is higher than 350 ° C., the polymer is decomposed by oxidation. On the other hand, the heat treatment after drying the solvent must be performed in an inert gas to suppress oxidative decomposition.
If the temperature is lower than ℃, there is a concern about outgassing from the film when forming the wiring. If the temperature is higher than 450 ℃, the polymer is thermally decomposed.

The insulating film forming material of the present invention is an organic resin, and is oxidized when exposed to oxygen plasma. Therefore, a situation in which the insulating film is directly exposed to the oxygen plasma, such as removing the resist by the oxygen plasma after patterning the insulating film formed from the insulating film forming material of the present invention using the resist, should be avoided. . For this purpose, a silicon oxide film (SiO ₂ film), a silicon nitride film, a PSG film, a SiON film, etc. are formed as a protective film on the low dielectric constant insulating film formed according to the present invention, and then a resist layer is formed. What is necessary is just to pattern it.

The semiconductor device of the present invention includes a semiconductor substrate and a plurality of insulating layers and a plurality of wiring layers formed alternately on the semiconductor substrate, and at least one of these insulating layers is formed of the present invention. This is a film made of a low dielectric constant insulating film forming material. This semiconductor device is free from the drawback that the wiring delay is reduced by incorporating the low dielectric constant insulating film according to the present invention, and the dielectric constant is increased due to moisture absorption over time.

The semiconductor device of the present invention also includes one obtained by forming the above protective film (that is, an oxidation-resistant film) on the insulating film of the present invention and flattening the same.

In the semiconductor device of the present invention, since copper does not diffuse in the insulating film formed by the present invention, the material of the metal wiring forming the wiring layer is selected from aluminum and an alloy mainly containing aluminum. Of course, it can also be selected from copper and alloys mainly composed of copper.
Further, in these wiring layers, titanium or an alloy mainly containing titanium, or tantalum or an alloy mainly containing tantalum may be used as a barrier metal.

[0032]

EXAMPLES Next, the present invention will be further described with reference to examples, but it goes without saying that the present invention is not limited to these examples.

Example 1 In a flask equipped with a stirrer, thermometer and dropping funnel, 10% aqueous sodium hydroxide solution (0.25 mol as NaOH) and 0.1 mol of 1,3- (adamandyl) phenol were added with methyl. Dissolved and charged in isobutyl ketone. Next, 0.1 mol of 1,4-dichlorobiphenyl dissolved in methyl isobutyl ketone was added dropwise, and the reaction system was heated to 80 ° C. and stirred for 2 hours. After cooling to room temperature, stirring was stopped, the lower layer was removed with a separating funnel, and the upper layer was repeatedly washed five times with pure water. After washing, the upper layer substance is removed from methyl isobutyl ketone with a rotary evaporator, dissolved in benzene, freeze-dried, and then polymerized by the following formula (p: q in the formula)
= 1: 1) in about 85% yield.

[0034]

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The weight average molecular weight of this polymer is 7,600
And its structure was confirmed by infrared spectroscopy.

Next, this polymer was dissolved in cyclohexanone to prepare a solution of about 20% to prepare a coating liquid for forming an insulating film.

Example 2 The coating solution prepared in Example 1 was applied to a silicon substrate by a spin coater at about 3000 ° (3
00nm) coated and dried on a hot plate at 250 ° C. for 3 minutes in a nitrogen atmosphere with an oxygen concentration of 25 ppm.
Heat treatment was performed at 400 ° C. for 30 minutes to form a film. A gold electrode having a diameter of 1 mm and a thickness of 0.1 μm was formed on this film, and the permittivity was calculated from the capacitance / voltage characteristics.
Met. Further, when the dielectric constant was observed over time in the air atmosphere (25 ° C., 60% relative humidity) for 7 days, the dielectric constant after 7 days was 2.5 (FIG. 1).

For comparison, an inorganic SO prepared by a sol-gel method on a silicon substrate using tetraethoxysilane was used.
When the change with time of the dielectric constant of the film G (comparative example) was observed under the same conditions, the dielectric constant after 7 days was increased (FIG. 1).

Example 3 The coating solution prepared in Example 1 was applied to a silicon substrate by a spin coater at about 3000 ° (3
00nm), and after drying the solvent for 3 minutes on a hot plate at 250 ° C., in a nitrogen atmosphere with an oxygen concentration of 25 ppm,
Heat treatment was performed at 400 ° C. for 30 minutes to form a film. Approximately 500 ° (50 n
m) A copper film was formed, and the carbon and copper atoms were analyzed for depth by X-ray electron spectroscopy (XPS). As a result, no copper was diffused into the film (FIG. 2).

For comparison, an inorganic SO prepared by a sol-gel method on a silicon substrate using tetraethoxysilane was used.
The copper film formed under the same conditions on the G film (comparative example) was subjected to depth analysis of silicon and copper atoms by XPS. As a result, copper atoms were diffused in the film (FIG. 2).

Example 4 The coating solution prepared in Example 1 was applied to a silicon substrate by a spin coater at about 3000Å (3
00nm) coated and dried on a hotplate at 250 ° C. for 3 minutes in a nitrogen atmosphere with an oxygen concentration of 25 ppm.
Heat treatment was performed at 400 ° C. for 30 minutes to form a film. The coating was subjected to degassing analysis using a heating and heating degassing analyzer. As a result, no organic degassing was observed up to 420 ° C., and good heat resistance was confirmed.

[0042]

As described above, according to the present invention,
It is possible to use an insulating film material that can obtain a highly reliable insulating film with a low dielectric constant. In a highly integrated semiconductor device using an insulating film formed from this material, a delay in signal propagation speed can be reduced with a decrease in the dielectric constant of the insulating film. Provision is possible.

[Brief description of the drawings]

FIG. 1 is a graph showing a change over time of a dielectric constant of an insulating film in comparison with an insulating film according to the present invention.

FIG. 2 is a graph showing a state of copper diffusion in an insulating film according to the present invention and a comparative insulating film.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yamaguchi Castle 4-1, 1-1 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Katsumi Suzuki 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Inside Fujitsu Limited

Claims (7)

[Claims] 1. An insulating film forming material, which is an arylene ether polymer containing an adamantane ring in a main chain skeleton. 2. The polymer has the following general formula: Wherein each R ^{A in the} formula is independently hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or a phenyl group;
R ¹ and R ² may be the same or different;
O- or the following formula: Wherein each R ³ is independently hydrogen or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and n is a weight average molecular weight of the polymer of 500 to 50,000. Or an integer of the following general formula: Wherein each R ^{A in the} formula is independently hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or a phenyl group;
R ⁵ and R ⁶ may be the same or different,
O- or the following formula: Wherein R ⁸ is —O— or a compound represented by the following formula: Is a divalent group represented by R ⁹ is hydrogen or carbon number 1
3 is a monovalent hydrocarbon group, p and q are such that the weight average molecular weight of the polymer is 500 to 50,000, and p: q
Is an integer such that = 1: 0.2 to 1: 2)
The insulating film forming material according to claim 1, wherein 3. A semiconductor device comprising a substrate and a plurality of insulating layers and a plurality of wiring layers formed alternately on the substrate, wherein at least one of the insulating layers has an adamantane in a main chain skeleton. A semiconductor device formed from an insulating film forming material of an arylene ether-based polymer containing a ring. 4. The polymer has the following general formula: Wherein each R ^{A in the} formula is independently hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or a phenyl group;
R ¹ and R ² may be the same or different;
O- or the following formula: Wherein each R ³ is independently hydrogen or a monovalent hydrocarbon group having 1 to 3 carbon atoms, and n is a weight average molecular weight of the polymer of 500 to 50,000. Or an integer of the following general formula: Wherein each R ^{A in the} formula is independently hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or a phenyl group;
R ⁵ and R ⁶ may be the same or different,
O- or the following formula: Wherein R ⁸ is —O—, or the following formula: Is a divalent group represented by R ⁹ is hydrogen or carbon number 1
3 is a monovalent hydrocarbon group, p and q are such that the weight average molecular weight of the polymer is 500 to 50,000, and p: q
Is an integer such that = 1: 0.2 to 1: 2)
The semiconductor device according to claim 3, wherein 5. The semiconductor device according to claim 3, further comprising an oxidation-resistant film formed on said insulating layer and planarized. 6. The semiconductor device according to claim 3, wherein the material forming the wiring layer is aluminum, an alloy mainly containing aluminum, copper, or an alloy mainly containing copper. . 7. The semiconductor device according to claim 6, wherein said wiring layer contains titanium, an alloy mainly composed of titanium, tantalum or an alloy mainly composed of tantalum as a barrier metal.