JPH1140554A - Insulating film forming material, and method for forming insulating film and semiconductor device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an insulating film of low dielectric constant and high reliability for raising response speed in a multi-layer interconnection structure with the insulating film employed, by using an insulating film formation material comprising siloxane composition containing a specific amount of siloxane of cage structure of Si8 . SOLUTION: An insulating film formation material comprising siloxane composition containing 50 vol.% or more of siloxane of cage structure of Si8 is prepared. The siloxane of cage structure of Si8 has a cubic structure represented by a constitutional formula (R coupled with each silicon is H, F, and organic group, and representative example of organic group includes methyl group, alkyl group of carbon numbers 1-6 such as ethyl group, alkenyl group of carbon numbers 1-6 such as vinyl group, and phenyme group), while silicon atom present at each vertex of cube and oxygen atom at intermediate of each side of cube. Relating to a film obtained from a siloxane containing organic group, H and F is suitable for R considering crack, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a material for forming an insulating film in multilayer wiring of a semiconductor integrated circuit, and a semiconductor device including the insulating film formed using the material.

[0002]

2. Description of the Related Art With the increase in the degree of integration of semiconductor integrated circuits and the increase in element density, demands for multi-layer semiconductor elements have been increasing. Further, in order to prevent an increase in wiring capacitance due to miniaturization of wiring, it is increasingly necessary to increase the thickness of wiring. For this reason, the level difference due to wiring in a semiconductor integrated circuit having a multilayer structure tends to be further increased.

On the other hand, the wiring delay (T) is the wiring resistance (R)
And the capacitance between the wirings (C), and if the wiring length is L, it is expressed by the following equation (1).

[0004]

(Equation 1)

If the dielectric constant of the insulating film is ε _r , the capacitance C between the wirings in the equation (1) is expressed by the following equation (2).

[0006]

(Equation 2)

In this equation, S is the electrode area, ε
₀ represents the dielectric constant of vacuum and d represents the film thickness. As is apparent from these equations, it is effective to reduce the dielectric constant of the insulating film to reduce the wiring delay T.

Conventionally, as an insulating material in a multilayer wiring of a semiconductor integrated circuit, an inorganic material such as silicon dioxide (SiO ₂ ), silicon nitride (SiN), and phosphosilicate glass (PSG), or an organic material such as polyimide and organic SOG has been used. Polymers have been used. However, in CVD-SiO ₂ film exhibiting the lowest dielectric constant in the film of an inorganic material, a dielectric constant of about 4. Further, a SiOF film which has been recently studied as a low dielectric constant CVD film and has a dielectric constant of about 3.3 to 3.5,
This film has a high hygroscopicity and has a problem that the dielectric constant increases during use.

On the other hand, an organic polymer film having a low dielectric constant of 2.5 to 3.0 has a glass transition temperature of 200 to 35.
Since the temperature is as low as 0 ° C. and the coefficient of thermal expansion is large, damage to the wiring is a problem. In addition, the organic SOG film is oxidized by oxygen plasma ashing used for stripping resist when forming a multilayer wiring pattern,
It has the disadvantage of cracking. Organic SOG
Is low in adhesion to wiring materials such as aluminum and alloys mainly composed of aluminum and copper and alloys mainly composed of copper, so that voids are formed beside the wiring (between the wiring and the insulating material). Gaps), which may lead to moisture penetration and lead to wiring corrosion. Furthermore, these wiring side voids may cause short-circuiting between wiring layers when misalignment occurs when opening a via hole for forming a multilayer wiring. Invited,
There is a problem that reduces reliability.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to form a highly reliable insulating film having a low dielectric constant in a multilayer wiring structure. Is to provide. It is also an object of the present invention to provide a method for forming an insulating film of a multilayer wiring using the insulating film forming material, and a highly reliable semiconductor device including the insulating film formed using the insulating film forming material. .

[0011]

The insulating film forming material of the present invention is characterized by comprising a siloxane composition containing at least 50 vol% of a siloxane having a cage structure of Si ₈ .

Further, in one method of forming an insulating film (first method) of the present invention, 50 v of siloxane having a cage structure of Si ₈ is used.
% or more of a siloxane composition containing a siloxane composition is applied to a substrate to form a film.
The first heat treatment is performed at the following temperature, and the second heat treatment is performed at a temperature higher than 300 ° C. and 450 ° C. or less to form an insulating film.

Another method (second method) for forming an insulating film according to the present invention is a method of forming a cage-type Si ₈ siloxane of 50 vol.
An insulating film forming material comprising a siloxane composition containing 1% or more is applied to a substrate to form a film, and 30%
The method is characterized in that an insulating film is formed by irradiating ultraviolet rays at a temperature of 0 ° C. or less.

Still another method (third method) of forming an insulating film according to the present invention is to form a cage-type siloxane of Si ₈ into 5
An insulating film forming material comprising a siloxane composition containing 0 vol% or more is applied to a substrate to form a film, and 30%
An insulating film is formed by irradiating ultraviolet rays at a temperature of 0 ° C. or lower and then performing a heat treatment at a temperature higher than 300 ° C. and 450 ° C. or lower.

Further, the semiconductor device of the present invention is a semiconductor device having a multilayer wiring structure formed by alternately stacking wiring layers and insulating layers, wherein 50% of siloxane having a cage structure of Si ₈ is used.
It is characterized by including an insulating film layer formed from an insulating film forming material made of a siloxane composition containing at least vol%.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a siloxane composition containing 50 vol% or more of a siloxane having a cage structure of Si ₈ is used as an insulating film forming material. Si ₈ cage-type siloxane is

[0017]

Embedded image

The silicon atom is present at each vertex of the cube, and the oxygen atom is present in the middle of each side of the cube. R bonded to each silicon atom in this formula is independently H, F, or an organic group. Representative examples of the organic group include an alkyl group having 1 to 6 carbon atoms (eg, a methyl group, an ethyl group, etc.),
6 alkenyl group (eg, vinyl group, etc.) or phenyl group. Since the film obtained from siloxane containing an organic group is oxidized by oxygen plasma ashing used for resist stripping in the process of forming a multilayer wiring structure of a semiconductor integrated circuit, it may cause cracks,
More preferred as R in the above formula is H or F.

Such a cage type siloxane of Si ₈ is represented by the following formula:

[0020]

Embedded image

Is produced as a by-product in the production of polysiloxanes generally referred to as ladder siroquines, where R is the same as above and n is a positive integer, represented by Usually, about 10 vol% is contained in the produced ladder siloxane. Ladder siloxane is sometimes used as an insulating film material for a multilayer wiring structure of a semiconductor integrated circuit. In this case, by-product Si
_{The one from which the} cage-type siloxane is removed is used.

The Si ₈ cage type siloxane used in the present invention may be used by concentrating or separating by-products produced during the production of ladder siloxane, or by using a specially synthesized product. Is also good. In order to concentrate or separate the by-product Si ₈ cage structure siloxane in the ladder siloxane, for example, a difference in solubility between the Si ₈ cage structure siloxane and the ladder siloxane in a specific solvent can be advantageously used.

Since the Si ₈ cage-type siloxane has minute spaces in cubic molecules as is apparent from the structural formula (1) shown above, a low-density insulating film is formed by polymerization by crosslinking. Formed, whereby the dielectric constant of the insulating film can be reduced. The insulating film obtained according to the present invention is made of Si ₈
Since R in the above formula (1) representing the cage type siloxane is an inorganic film as long as it does not contain an organic group, it is not oxidized by oxygen plasma during the resist ashing process. Further, R
Is H, since the Si—H bond is water repellent, it is possible to effectively suppress an increase in the dielectric constant due to moisture absorption as observed in the CVD-SiOF film. Therefore,
According to the present invention, a semiconductor integrated circuit having a high response speed can be obtained.

Shiroki constituting the insulating film forming material of the present invention
The sun composition is Si₈Low siloxane component in cage structure
There is no particular limitation as long as it contains at least 50 vol%. S
i₈As a siloxane component other than the cage type siloxane
Are, for example, the ladder siloxanes mentioned above,
Siloxane that can form an insulating film by gel method or
It is possible to use any mixture of siloxanes such as
it can. In this case, Si ₈Other than cage-type siloxane
The loxane component also has more H than the one having an organic group in the side chain.
Or it is preferable to use one having F.

When an insulating film is formed by the first method of the present invention, the insulating film forming material of the present invention is applied to a substrate (usually a substrate having metal wiring) by, for example, a spin coating method. By performing the first heat treatment at a temperature of 300 ° C. or less, the solvent is dried and the siloxane having the Si ₈ cage structure is crosslinked (at this time, the crosslinking of the siloxane component other than the Si ₈ cage structure siloxane also proceeds). Next, a second heat treatment (annealing) is performed at a temperature higher than 300 ° C. and 450 ° C. or lower, whereby an insulating film having a low dielectric constant can be formed. The reason why the first heat treatment is set to 300 ° C. or lower is to facilitate the adjustment of the degree of cross-linking so that the cross-linking does not proceed excessively, and to set the second heat treatment to a temperature higher than 300 ° C. and 450 or lower. Is because this temperature range is generally convenient for annealing.

The crosslinking of the siloxane by the first heat treatment is as follows:
This first heat treatment can be advantageously performed in the air since the progress is made by the formation of a Si—O—Si bond by oxidation. In addition, the degree of crosslinking may be adjusted to adjust the dielectric constant of the formed insulating film, and the adjustment of the degree of crosslinking can be performed by adjusting the heat treatment temperature and time.

The second heat treatment for annealing is preferably performed in an inert gas containing 1% or less of oxygen or in a vacuum. This is to prevent hydrogen or fluorine bonded to Si, which is left after adjusting the degree of crosslinking in the first heat treatment, from being reduced by oxidation during the second heat treatment.

In the second method of the present invention, the siloxane containing hydrogen bonded to silicon forms a Si—O—Si bond when irradiated with ultraviolet rays in the air, and the crosslinking proceeds. UV irradiation is performed. In this case, the treatment temperature is preferably 300 ° C. or less. This is because heating to a temperature exceeding 300 ° C. causes excessive cross-linking due to oxidation, and reduces hydrogen and fluorine bonded to silicon of the siloxane. This leads to an increase in the dielectric constant of the insulating film.

In the third method of the present invention, in addition to the ultraviolet irradiation in the second method, a heat treatment at a temperature higher than 300 ° C. and 450 ° C. or less is performed. This heat treatment corresponds to the second heat treatment (annealing) in the first method, and is also preferably performed in an inert gas containing 1% or less of oxygen or in a vacuum.

On the insulating film formed according to the present invention, another insulating film such as a silicon oxide film may be formed by using, for example, a vapor growth method. This is effective in shutting off the insulating film formed according to the present invention from outside air and suppressing a decrease in hydrogen and fluorine remaining in the film. This other insulating film is also effective in preventing the insulating film according to the present invention from being damaged in a subsequent process (for example, a process such as planarization by chemical mechanical polishing).

According to the present invention, there is provided a multilayer wiring structure formed by alternately laminating wiring layers and insulating layers, wherein at least one of the insulating layers is made of 50% Si ₈ cage-type siloxane.
A semiconductor device including a low-dielectric-constant insulating film layer formed from an insulating film-forming material made of a siloxane composition containing at least vol% is obtained. In the semiconductor device according to the present invention, the speed can be increased by lowering the dielectric constant of the insulating film, and the increase in the dielectric constant due to moisture absorption is suppressed, and the reliability is improved.

[0032]

Next, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

Example 1 A siloxane composition containing 50 vol% of a Si ₈ cage-type siloxane in which R in the above formula (1) is hydrogen (the remaining siloxane has a molecular weight of 3 represented by the above formula (2)) 4,000 ladder siloxanes,
A 15 wt% solution of methyl isobutyl ketone (R in the formula is hydrogen) was placed on a silicon substrate at 2500 ° (250 n).
m) Spin-coat and place on a hot plate in the air for 20 minutes.
Heat treatment was performed at 0 ° C. for 3 minutes to crosslink the siloxane, and the solvent was dried. Next, in various types of nitrogen each containing 0.001% to 10% of oxygen, 40
Heat treatment was performed at 0 ° C. for 30 minutes to form an insulating film. The dielectric constant of the obtained insulating film was as shown in FIG. In addition,
The dielectric constant in this example and each of the following examples was obtained by calculating the capacitance between wirings using a capacitance meter and calculating by the formula (II).

Example 2 The siloxane composition used in the siloxane composition had a Si ₈ cage structure in which R in the formula (1) was hydrogen and fluorine (hydrogen: fluorine ratio = 1: 1). Example 1 was repeated, except for this. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 3 Example 1 was repeated, except that the siloxane of the Si ₈ cage structure in the siloxane composition used was changed to a compound in which R in the formula (1) was fluorine. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 4 A 15 wt% solution of the siloxane composition used in Example 1 in methyl isobutyl ketone was spin-coated on a silicon substrate at 2500.degree. (250 nm), and ultraviolet rays were irradiated on a hot plate at 200.degree. For a minute to crosslink the siloxane,
Solvent drying was performed. Next, each oxygen is 0.001%
In various kinds of nitrogen containing from 10% to 10%, heat treatment was performed at 400 ° C. for 30 minutes to form an insulating film. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 5 The siloxane composition used in the siloxane composition had a Si ₈ cage type siloxane in which R in the formula (1) was hydrogen and fluorine (hydrogen: fluorine ratio = 1: 1). Example 4 was repeated, except for this. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 6 Example 4 was repeated, except that the siloxane of the Si ₈ cage structure in the siloxane composition used was changed to a compound in which R in the formula (1) was fluorine. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 7 A 15 wt% solution of the siloxane composition used in Example 1 in methyl isobutyl ketone was spin-coated at 2500 ° C. (250 nm) on a silicon substrate and heated at various heating temperatures from 150 ° C. to 400 ° C. Ultraviolet rays were irradiated on the plate in the air for 5 minutes to crosslink the siloxane, and the solvent was dried to form an insulating film. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 8 The siloxane having a cage structure of Si ₈ in the siloxane composition used was changed to a compound in which R in the formula (1) was hydrogen and fluorine (hydrogen: fluorine ratio = 1: 1). Example 7 was repeated, except for this. The dielectric constant of the obtained insulating film was as shown in FIG.

Example 9 Example 7 was repeated, except that the siloxane of the Si ₈ cage structure in the siloxane composition used was changed to a compound in which R in the formula (1) was fluorine. The dielectric constant of the obtained insulating film was as shown in FIG.

[0042]

As described above, according to the present invention,
A highly reliable insulating film having a low dielectric constant can be obtained. Further, by adopting this insulating film, the response speed in the multilayer wiring structure can be improved, and the performance of the semiconductor device including the multilayer wiring can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of Examples 1 to 3.

FIG. 2 is a graph showing the results of Examples 4 to 6.

FIG. 3 is a graph showing the results of Examples 7 to 9.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Rinko Katayama 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Shiro Yamaguchi 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture No. 1 Inside Fujitsu Limited

Claims (11)

[Claims] 1. The following formula: (R in this formula are each independently hydrogen, fluorine, alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a phenyl group) cage structure of Si _8, represented by An insulating film forming material comprising a siloxane composition containing 50 vol% or more of the siloxane. 2. The insulating film-forming material according to claim 1, wherein R in the formula of the cage-type siloxane of Si ₈ is hydrogen. 3. The insulating film forming material according to claim 1, wherein R in the formula of the siloxane having a cage structure of Si ₈ is hydrogen and fluorine. 4. The insulating film forming material according to claim 1, wherein R in the formula of the cage-type siloxane of Si ₈ is fluorine. 5. The following formula: (R in this formula are each independently hydrogen, fluorine, alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a phenyl group) cage structure of Si _8, represented by An insulating film forming material comprising a siloxane composition containing 50 vol% or more of the siloxane is applied to a substrate to form a film, and the film is subjected to a first heat treatment at a temperature of 300 ° C. or less, and then to a temperature higher than 300 ° C. and 450 ° C. An insulating film forming method, wherein a second heat treatment is performed at the following temperature to form an insulating film. 6. The following formula: (R in this formula are each independently hydrogen, fluorine, alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a phenyl group) cage structure of Si _8, represented by A siloxane composition containing a siloxane composition containing 50 vol% or more of the above siloxane composition to a substrate to form a film, and irradiating the film with ultraviolet rays at a temperature of 300 ° C. or less to form an insulating film. Insulating film forming method. 7. The following formula: (R in this formula are each independently hydrogen, fluorine, alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a phenyl group) cage structure of Si _8, represented by An insulating film forming material comprising a siloxane composition containing 50 vol% or more of the above siloxane is applied to a substrate to form a film, and this film is irradiated with ultraviolet rays at a temperature of 300 ° C. or less, and then heated to a temperature higher than 300 ° C. and 450 ° C. or less. A method for forming an insulating film, comprising: performing heat treatment at a temperature to form an insulating film. 8. The method according to claim 5, wherein the heat treatment at a temperature higher than 300 ° C. and not higher than 450 ° C. is performed in an inert gas having an oxygen content of 1% or lower or in a vacuum. 9. The method according to claim 5, wherein R in the formula of the Si ₈ cage structure siloxane is one or both of hydrogen and fluorine. 10. A semiconductor device including a multilayer wiring structure formed by alternately stacking wiring layers and insulating layers, wherein the semiconductor device has the following formula: (R in this formula are each independently hydrogen, fluorine, alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a phenyl group) cage structure of Si _8, represented by A semiconductor device comprising an insulating film layer formed from an insulating film forming material made of a siloxane composition containing 50 vol% or more of the siloxane. 11. The semiconductor device according to claim 9, wherein R in the formula of the siloxane having a cage structure of Si ₈ is one or both of hydrogen and fluorine.