JPH1154498A - Insulating film of low dielectric constant, formation thereof, and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new fluorocarbon-based insulation film having a low dielectric constant and improved contactability with a metal wiring, by providing an organic silicon polymer layer containing an organic group for which fluorine is substituted between a fluorocarbon polymer layer and a metal wiring layer. SOLUTION: An aluminum wiring layer is formed on the surface of a silicon substrate 1, and a first layer 2 of fluorinated organic silicon polymer is formed on the aluminum wiring layer. An amorphous fluorocarbon polymer layer 3 is formed thereon. A second layer 4 of fluorinated organic silicon polymer is formed on this amorphous fluorocarbon polymer layer 3, thus constituting an insulating film 5 made up of a multilayered body of the layers 2, 3 and 4. The lower surface of the silicon substrate 1 and the upper surface of the insulating film 5 are adhered to tension jigs 9 and 9' with adhesives 8 and 8', respectively. The jigs 9 and 9' are tensioned in opposite directions, and the separating force between the insulating film 5 and the aluminum wiring layer is used for contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an insulating film in a multilayer wiring structure of a semiconductor integrated circuit. According to the method for forming an insulating film of the present invention, an interlayer insulating film having a low dielectric constant and excellent moisture resistance can be obtained, so that a highly reliable high-speed device can be provided.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for faster electronic devices. In order to increase the speed of the device, it is necessary to reduce the wiring delay by lowering the wiring resistance and lowering the dielectric constant of the interlayer insulating film having a multilayer wiring structure.

In order to realize a high-speed device by lowering the dielectric constant of an interlayer insulating film, conventionally, as a material of the interlayer insulating film, an inorganic material such as silicon dioxide, silicon nitride, PSG, or a polyimide, silicone resin, or the like is used. Organic polymer insulating materials, or a laminate thereof. Among these, the dielectric constant of the inorganic material is about 4.0 for SiO ₂ , which has the lowest dielectric constant among CVD materials, and is 2.5 to 3.0, which is the general dielectric constant of organic polymer materials. taller than. Further, SiOF, which is studied as a low dielectric constant inorganic CVD material, has a value of about 3.0 to 3.5, but this material has a problem that the dielectric constant gradually increases due to moisture absorption. Organic Meanwhile, relatively permittivity organic polymer material being a low, it is difficult to fine processing in the conventional method, also in the O ₂ plasma treatment is utilized such as resist stripping in the manufacturing process of a semiconductor device It has the disadvantage that the groups are oxidized. Further, a fluorocarbon polymer is known as a material that does not cause oxidative decomposition in the O ₂ plasma treatment, but this material has been inferior in adhesion to metal wiring and has been difficult to be put into practical use.

[0004]

As described above, various approaches to increase the speed of a semiconductor integrated circuit by lowering the dielectric constant of an interlayer insulating film having a multilayer wiring structure have their own problems. is there. Among them, the approach using fluorocarbon-based polymers is noteworthy because this material has a lower dielectric constant than inorganic materials and is more resistant to O ₂ plasma treatment. However, this material is difficult to use as a single layer because of its poor adhesion to metal wiring as described above compared to other low dielectric constant materials, and it is difficult to use this material between metal wiring layers. It is necessary to provide another layer for ensuring adhesion. The adhesion layer to ensure this adhesion is
In order not to negate the advantage of using a fluorocarbon-based polymer for the interlayer insulating film, it is essential that the dielectric constant itself be as low as possible.

Accordingly, an object of the present invention is to provide a new fluorocarbon-based insulating film having a low dielectric constant and improved adhesion to a metal wiring, and a method for forming the insulating film. It is another object of the present invention to provide a semiconductor device including an insulating film having a low dielectric constant and a high adhesion formed by this method.

[0006]

An insulating film according to the present invention is a film constituting an insulating layer in a multilayer wiring structure in which a metal wiring layer and an insulating layer are laminated, and comprises a fluorocarbon polymer layer, And a layer of an organic silicon polymer containing a fluorine-substituted organic group interposed between the wiring layer and the wiring layer.

The method of forming an insulating film according to the present invention comprises forming an insulating film comprising a fluorocarbon polymer layer and a layer of an organic silicon polymer containing a fluorine-substituted organic group, adjacent to at least one surface of the layer. Forming a starting organic silicon polymer into a film and then performing a fluorination treatment to at least partially replace the organic groups of the starting organic silicon polymer with fluorine, thereby containing the fluorine-substituted organic group. And forming an organic silicon polymer layer.

A semiconductor device according to the present invention is a semiconductor device having a multilayer wiring structure formed by alternately laminating metal wiring layers and insulating layers, wherein the insulating layers are a fluorocarbon polymer layer, the fluorocarbon polymer layer and the fluorocarbon polymer layer. It is characterized by comprising an insulating film comprising an organic silicon polymer layer containing a fluorine-substituted organic group interposed between the wiring layer and the wiring layer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an interlayer insulating film of a multilayer wiring structure
Useful insulating films of the invention have low dielectric constants and O _Twoplasma
Fluorocarbon polymer layer resistant to processing
And the fluorocarbon polymer layer and the adjacent metal wiring layer
Contains a fluorine-substituted organic group interposed between
Organosilicon polymer (the description will be simplified below)
Therefore, it will be called "fluorine-substituted organosilicon polymer".
Layer).

As the material for the fluorocarbon polymer layer, any fluorocarbon polymer can be used. As an example, amorphous fluorocarbon (α-CF) well known in the semiconductor device industry can be used, and the α-CF layer can be easily formed by, for example, chemical vapor deposition using plasma.

In the insulating film of the present invention, a fluorine-substituted organic silicon polymer layer is disposed between the fluorocarbon polymer layer and the adjacent metal wiring layer. This polymer layer can be obtained by forming a coating of the corresponding starting organosilicon polymer and then fluorinating it. When the wiring layer exists below the insulating layer, the fluorine-substituted organosilicon polymer layer is formed before forming the fluorocarbon polymer layer, and when the wiring layer exists on the insulating layer, the fluorocarbon polymer layer is formed. After forming the layer, a fluorinated organosilicon polymer layer is formed thereon. not to mention,
The fluorine-substituted organosilicon polymer layer is arranged above and below the fluorocarbon polymer layer when metal wiring layers are arranged above and below the insulating layer.

The fluorine-substituted organosilicon polymer layer is formed by fluorinating the corresponding starting organosilicon polymer,
This starting organic silicon polymer may be any organic silicon polymer as long as it does not contain a siloxane bond (Si-O-Si bond) in the molecule and has an organic group that can be fluorinated after film formation. Representative examples of the organosilicon polymer useful as a starting polymer of the fluorine-substituted organosilicon polymer layer of the insulating film of the present invention are represented by the following formula:

[0013]

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Wherein R is hydrogen, a non-aromatic hydrocarbon group having 1 to 3 carbon atoms, or an aromatic hydrocarbon group, which is bonded to one silicon atom. At least one of the two R groups is a hydrocarbon group other than hydrogen, and R's are each independently hydrogen, a group having 1 carbon atom.
To 3 or an aromatic hydrocarbon group, and n is a positive integer. A typical example of the hydrocarbon group is an alkyl group such as a methyl group and an ethyl group, and a typical example of the aromatic hydrocarbon group is a phenyl group.

Regarding the case where polycarbosilane is used as the starting organosilicon polymer, the substrate on which the insulating film of the present invention is to be formed (the case where a metal wiring layer exists on the surface of the substrate and the case where the insulating film of the present invention is used) A fluorocarbon polymer layer of the film is present), and then form a film of the polycarbosilane, and then perform a fluorination treatment to at least part of the hydrogen atoms of the organic groups of the polycarbosilane. Is replaced by fluorine. This fluorination treatment for fluorine substitution can be performed by exposing the polycarbosilane coating to, for example, fluorine plasma.

The organosilicon polymer, such as polycarbosilane, which is the starting polymer of the fluorine-substituted organosilicon polymer, has a substantially lower dielectric constant than the inorganic insulating film material,
It has no hygroscopicity which causes an increase in the dielectric constant as shown by SiOF, and is excellent in flatness. However, these characteristics are not lost even after the fluorination treatment and the organic group is substituted with fluorine. The organic silicon polymer in which the organic group has been substituted with fluorine has a further lower dielectric constant than the starting polymer, and exhibits a stronger adhesion to the metal material than the fluorocarbon polymer. Therefore, by inserting such a layer having a low dielectric constant and a high adhesive force between the fluorocarbon polymer layer and the wiring layer, the effect of lowering the dielectric constant by the fluorocarbon polymer layer can be canceled without canceling the insulating layer and the metal. Adhesion with the wiring layer can be increased.

The fluorine-substituted organic silicon layer of the insulating film of the present invention may be generally much thinner than the fluorocarbon polymer layer, and may have a thickness of, for example, about 0.05 to 0.2 μm. On the other hand, the fluoropolymer layer is formed to have a predetermined thickness so as to obtain a predetermined interlayer insulating effect.

According to the present invention, it is possible to realize a semiconductor device including a multilayer wiring structure formed by alternately laminating metal wiring layers and insulating layers having a low dielectric constant and excellent adhesion to the wiring layers. Become. This semiconductor device can operate at high speed because the insulating layer has a low dielectric constant. In addition to ensuring the adhesion between the insulating layer and the wiring layer, the semiconductor device has a dielectric constant due to moisture absorption of the insulating layer over time. Since the insulating layer has resistance against O ₂ plasma, high reliability can be obtained.

[0019]

Next, the present invention will be further described with reference to examples.
It is noted that the invention is not in any way limited to these examples.
Needless to say.

[Embodiment 1] Wiring thickness of 8000Å (800n)
m), a fluorinated organic silicon polymer (hereinafter referred to as “S”) is formed on a silicon substrate provided with aluminum wiring having a wiring width of 0.5 μm.
iCF ") (0.1 μm thick)
And a layer (0.5 μm thick) of an amorphous fluorocarbon polymer (hereinafter abbreviated as “α-CF”);
An insulating film having a laminated structure composed of a second layer of SiCF (thickness: 0.1 μm) was formed under the following conditions.

The SiCF layer has the following formula

[0022]

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A 20 wt% xylene solution of polycarbosilane (average molecular weight 3000) represented by the following formula is spin-coated on a substrate, prebaked at 150 ° C. in a nitrogen atmosphere, and then subjected to fluorine by a down-flow type plasma generator. It was formed by performing a plasma treatment. The conditions of this fluorine plasma treatment were as follows. Applied power 1.5 kW Pressure 1.0 Torr (133 Pa) Substrate temperature 170 ° C. Gas NF ₃

The α-CF layer was formed using a parallel plate type plasma apparatus under the following conditions. Applied power 13.56 MHz, 100 W Pressure 1.0 Torr (133 Pa) Substrate temperature 400 ° C. Gas C ₂ H ₂ 20 sccm C ₄ F ₈ (cyclobutane) 100 sccm O ₂ 50 sccm

An electrode was formed on the formed laminated insulating film, and the dielectric constant was measured. The result was 2.3 (1 MHz).
Further, even after being left in the air for two weeks, no increase in the dielectric constant of the insulating film was observed.

Further, a tensile test was performed to evaluate the adhesion of the insulating film to the aluminum wiring layer. This test was conducted by preparing a tensile test sample as shown in FIG. In FIG. 1, reference numeral 1 denotes a substrate on which an aluminum wiring layer (not shown) is formed, 2 denotes a SiCF layer formed on the aluminum wiring layer, 3 denotes an α-CF layer formed thereon, Is an SiCF layer further formed thereon, and a laminate of these 2, 3, and 4 constitutes an insulating film 5 according to the present invention. The lower surface of the substrate 1 (the surface without the insulating film 5) and the upper surface of the insulating film 5 were bonded to the tensile jigs 9 and 9 'with adhesives 8 and 8', respectively. By pulling both jigs 9 and 9 ′ in opposite directions, the force required to peel the SiCF layer 2 of the insulating film 5 from the aluminum wiring layer in contact was measured and defined as the adhesion force. As a result of the test, the insulating film of the SiCF / α-CF / SiCF laminated structure of the present invention was about 5 times smaller than the comparative insulating film consisting of a single α-CF film.
It showed twice the adhesion.

[Embodiment 2] On a substrate on which five ring insulators are formed, an insulating film having a SiCF / α-CF / SiCF laminated structure of the present invention is formed under the same conditions as in Embodiment 1, and this insulating film is formed. After forming a through-hole so that a ring insulator is connected in series to the film, a substrate formed up to the second-layer wiring and tetraethoxysilane (TE) as a comparative sample
A substrate using an SiO ₂ insulating film formed from OS) was manufactured. As a result of comparing the wiring delays of the respective substrates, it was found that the wiring delay of the substrate using the insulating film according to the present invention can be reduced by about 25%.

Comparative Example Using a parallel plate type plasma apparatus, an SiOF film having a thickness of about 0.5 μm was formed on an Si substrate provided with the same aluminum wiring layer as used in Example 1 under the following conditions. did. Applied power 13.56 MHz, 100 W Pressure 1.0 Torr (133 Pa) Substrate temperature 350 ° C. Gas TEOS 100 sccm C ₄ F ₈ 300 sccm O ₂ 100 sccm

An electrode was formed on the formed insulating film, and the dielectric constant was measured. The result was 3.1 (1 MHz). However, after two weeks in air, the dielectric constant rose to 3.8.

[0030]

As is apparent from the above description, the present invention makes it possible to use an insulating film having a low dielectric constant and excellent adhesion, which is effective in reducing wiring delay in a multilayer wiring structure. Thus, a high-speed device can be realized and a highly reliable semiconductor device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a sample manufactured for a tensile test in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Aluminum wiring board 2, 4 ... Fluorinated organic silicon polymer layer 3 ... Amorphous fluorocarbon polymer layer 5 ... Insulating film 8, 8 '... Adhesive 9, 9' ... Tensile jig

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Yoshihiro Nakata 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 (8)

[Claims] 1. A film constituting an insulating layer in a multilayer wiring structure in which a metal wiring layer and an insulating layer are laminated, comprising: a fluorocarbon polymer layer; and a fluorine film interposed between the fluorocarbon polymer layer and the wiring layer. An organic silicon polymer layer containing a substituted organic group. 2. The organosilicon polymer containing a fluorine-substituted organic group is represented by the following formula: Wherein R is hydrogen, a non-aromatic hydrocarbon group having 1 to 3 carbon atoms, or an aromatic hydrocarbon group, wherein two R groups bonded to one silicon atom are represented by At least one of them is a hydrocarbon group other than hydrogen, and R ′
Is each independently hydrogen, a hydrocarbon group having 1 to 3 carbon atoms,
Or an aromatic hydrocarbon group, wherein n is a positive integer), obtained by fluorinating the insulating film. 3. The hydrocarbon group R is a methyl group,
The insulating film according to claim 2, wherein R 'is hydrogen. 4. A method for forming an insulating film comprising a fluorocarbon polymer layer and a layer of an organosilicon polymer containing a fluorine-substituted organic group adjacent to at least one surface of the layer, An organic silicon polymer layer containing the fluorine-substituted organic group by subjecting the starting organic silicon polymer to film formation and then fluorinating to at least partially replace the organic groups of the starting organic silicon polymer with fluorine; Forming an insulating film. 5. The starting organosilicon polymer has the following formula: Wherein R is hydrogen, a non-aromatic hydrocarbon group having 1 to 3 carbon atoms, or an aromatic hydrocarbon group, wherein two R groups bonded to one silicon atom are represented by At least one of them is a hydrocarbon group other than hydrogen, and R ′
Is each independently hydrogen, a hydrocarbon group having 1 to 3 carbon atoms,
Or an aromatic hydrocarbon group, and n is a positive integer). 6. The hydrocarbon group R is a methyl group,
The method of claim 5, wherein R 'is hydrogen. 7. The method according to claim 4, wherein the fluorination of the starting organosilicon polymer is performed by plasma using fluorine gas. 8. A semiconductor device including a multilayer wiring structure formed by alternately stacking metal wiring layers and insulating layers, wherein the insulating layer is formed between a fluorocarbon polymer layer and the fluorocarbon polymer layer and the wiring layer. And an organic silicon polymer layer containing a fluorine-substituted organic group interposed therebetween.