JPH09223739A - Insulating film of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an insulating film wherein permittivity is low, heat resistance is high, and possibility like pollution of fluorine ions does not exist, by using an insulating film composed of 2,6-diphenyl phenol polymer, for insulation between interconnection layers of a semiconductor device having a multilayer interconnection structure. SOLUTION: In a semiconductor device having a multilayer interconnection structure, an insulating film composed of 2,6-diphenyl phenol polymer is contained in an interlayer insulating film. The insulating film which has uniform quality and a thickness of about 1μm is formed on a first interconnection layer 3 which is composed of aluminum and formed on a semiconductor substrate. A connection hole for electrical connection with a second interconnection conductor layer 6 is formed by using dry etching technique, and then filled by CVD of tungsten. The second interconnection conductor layer 6 is formed on the insulating film by using sputtering and a photolithography method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating film between wiring layers of a semiconductor device having a multilayer wiring structure and a semiconductor device using the film.

[0002]

2. Description of the Related Art The most commonly used conventional multilayer wiring structure is a chemical vapor deposition (CVD) method as an insulator layer existing between a first wiring conductor layer and a second wiring conductor layer. A silicon dioxide film formed by the above is used. However, as the density and integration of semiconductor devices have increased, wiring has become finer and multilayered, and in the multilayer wiring structure formed by the conventional method, signal delay in the wiring layer,
Crosstalk is becoming a problem. Therefore, in order to solve these problems, organic polymers such as polyimide and fluoropolymers have been proposed as the interlayer insulating film. However, conventional polyimide has high heat resistance, but has problems in dielectric constant and hygroscopicity. Further, although fluorine-based polymers have low dielectric constant and hygroscopicity, they have problems in heat resistance and adhesiveness. Further, although a fluorinated aromatic polymer has been proposed in response to this, although heat resistance is improved, problems such as adhesiveness and contamination with fluorine ions still remain, and a satisfactory one is not obtained yet. The current situation. Further, the fluorine-containing polymer is generally expensive, and the device using the same becomes expensive. Therefore, the conventional method of doping silicon dioxide with fluorine is about to be put into practical use, but the lower limit of the dielectric constant is 3.
It is set to about 5, and in the future, an organic polymer having a lower dielectric constant and free from the above problems is desired.

Poly 2,6-diphenylphenol is known to be a material having high heat resistance and excellent dielectric properties. Macromolecules, 3 P.533 (1970), Macrolecul
es, 4 P.642 (1971) etc., describes them.
However, when it is used as an insulating film of a semiconductor device, thin film formability is an essential requirement, and attempts were made to form a homogeneous thin film of poly 2,6-diphenylphenol by various methods, but it was not possible to obtain a homogeneous thin film. There wasn't.

[0004]

DISCLOSURE OF THE INVENTION The present invention has a problem that it can be used as a wiring interlayer insulating film of a semiconductor device having a multilayer wiring structure, has a low dielectric constant and high heat resistance, and is derived from a fluorine atom. The purpose of the present invention is to provide an insulating film that is free from concerns such as adhesiveness and contamination with fluorine ions.

[0005]

The present inventors have found that poly-2,
As a result of extensive studies on a method of imparting thin film-forming property without impairing heat resistance and dielectric properties of 6-diphenylphenol, it was found that this object can be achieved by using a copolymer having a specific composition, and the present invention is completed. Came to.
That is, the present invention is as follows. (1) An insulating coating made of a 2,6-diphenylphenol copolymer used for insulation between wiring layers of a semiconductor device having a multilayer wiring structure. (2) The 2,6-diphenylphenol copolymer is
50-98% by weight of 2,6-diphenylphenol,
The insulating coating film according to 1 above, which is obtained by polymerizing 50 to 2% by weight of a phenolic monomer copolymerizable with 2,6-diphenylphenol and has a weight average molecular weight of 2000 or more and 500000 or less. (3) A polymer dope used in the production of the insulating film of 1 or 2 above, which comprises a 2,6-diphenylphenol copolymer and the solvent. (4) In a semiconductor device having a multilayer wiring structure, at least one layer of a wiring interlayer insulating coating of the semiconductor device is the insulating coating of 1 or 2 above.

According to the present invention, in a semiconductor device having a multilayer wiring structure, the wiring interlayer insulating coating includes an insulating coating made of a 2,6-diphenylphenol copolymer. This 2,6-diphenylphenol copolymer is 2,6-diphenylphenol, 2,
It is obtained by polymerizing 6-diphenylphenol and a copolymerizable phenolic monomer, and the polymerization rates thereof are 50 to 98% by weight and 50 to 2% by weight, respectively, and preferably 70 to 95% by weight and 30 to respectively. It is 5% by weight.
When the amount of 2,6-diphenylphenol is less than 50% by weight, the heat resistance is insufficient and it is not preferable when used in a semiconductor device. If it is more than 98% by weight, a uniform film cannot be formed during thin film formation.

The comonomer used in the 2,6-diphenylphenol copolymer of the present invention may be any phenolic monomer copolymerizable with 2,6-diphenylphenol, such as 2,6-dimethylphenol. Two
-Methyl-6-allylphenol, orthohydroxybiphenyl and the like can be mentioned. The molecular weight of the 2,6-diphenylphenol copolymer is gel permeation
It is measured by chromatography (GPC) and has a polystyrene-equivalent weight average molecular weight of 2,000 or more and 50,000 or more.
It is 0 or less, preferably 5000 or more and 300,000 or less. If it is less than 2000, the coating film is not formed or a coating film having sufficient strength cannot be obtained. Further, when the molecular weight is larger than 500000, the solution viscosity becomes too high at the solution concentration necessary to obtain a desired film thickness during the preparation of the polymer dope, which causes a problem in handling.

The 2,6-diphenylphenol copolymer used in the present invention is synthesized by dissolving 2,6-diphenylphenol and its comonomer in a solvent and oxidatively polymerizing with oxygen in the presence of a catalyst. Examples of the solvent used at this time include aromatic hydrocarbons such as benzene and toluene, and halogenated aromatic hydrocarbons such as o-dichlorobenzene. Among them, in the present invention, halogen-free benzene, toluene and the like are included. preferable. As the catalyst used, a combination of copper halide and amine is preferable, and particularly copper bromide and N, N, N ', N'.
A combination of tetramethyl-1,3-butanediamine is preferred. The copper halide and the amine are used in equimolar amounts, and the amount used is 0.01 per mol of the monomer.
Is in the range of 0.1 mol. Since water is generated in the system as the reaction progresses, a dehydrating agent such as magnesium sulfate is also added to remove it. The reaction is carried out by blowing oxygen into the system at room temperature, but cooling or heating may be performed depending on the situation. After completion of the reaction, the polymer can be reprecipitated by filtering the insoluble matter in the reaction solution and then dropping it into a poor solvent such as methanol or isopropyl alcohol. The polymer obtained by this precipitation can be purified by re-dissolving it in an aromatic hydrocarbon solvent such as benzene or toluene, and then repeating the above operation.

The insulating coating of the present invention is formed by using a spinner or the like after dissolving the above polymer in a predetermined solvent to form a polymer dope. The solvent used for preparing the polymer dope is preferably a non-halogen solvent capable of dissolving the polymer and having a relatively high boiling point, such as N-methylpyrrolidone, amide solvents such as N, N-dimethylacetamide, and toluene. Aromatic solvent, cyclohexanone,
Examples thereof include ketone solvents such as cyclopentanone, and of these, amide solvents such as N-methylpyrrolidone and N, N-dimethylacetamide are particularly preferable. Further, these solvents may be mixed and used, or a polar solvent such as alcohol may be mixed for the purpose of improving coating characteristics.

The concentration of the polymer dope obtained by dissolving in these solvents depends on the required film thickness and
Depending on the molecular weight of the 6-diphenylphenol copolymer,
Usually, those in the range of 5 to 20% by weight are used. If it is less than 5% by weight, it is difficult to obtain a uniform film having a low concentration. If the concentration is within this range, an insulating film having a desired film thickness can be easily formed by spin coating.

If necessary, a silicon-based adhesion aid or the like may be added to the polymer dope in order to enhance the adhesion to the substrate. The obtained polymer dope is used after being filtered with a 0.1 μm filter, but since it is relatively stable and shows no deterioration in performance even at room temperature, it can be stored and used. However, it is desirable to store in a cool dark place for a long period of one week or more.

The polymer dope thus obtained is formed into a film by a spinner or the like to obtain the insulating film of the present invention. The number of rotations when spin-coating the polymer dope on the substrate is 800-
A range of 6000 rpm is preferred. The coating film applied on the substrate is dried at 50 to 250 ° C., and if necessary, heat treatment may be performed at a higher temperature. The film thickness of the coating film thus obtained is measured by a contact type or non-contact type film thickness meter, and is usually used in the range of 0.2 to 2 μm, preferably 0.5 to 1.5 μm. is there.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments. The weight average molecular weight of the 2,6-diphenylphenol copolymer was measured by GPC and calculated in terms of polystyrene. For the film thickness of the film, a contact-type film thickness meter (DEKTAKII manufactured by Sloan Co., Ltd.) was used, and the heat resistance was determined by a thermobalance
Shimadzu TGA-5O) was used and the measurement was performed in nitrogen. The dielectric constant of the coating is measured by the shield microprobe method (HP4280 manufactured by Yokogawa / Hewlett-Packard Co.).
It was measured according to A).

[0014]

[Example 1] 300 ml equipped with an oxygen introduction tube and a stirring device
160 ml of benzene was weighed into a flask, and 0.288 g of copper bromide, 0.284 g of N, N, N ', N'-tetramethyl-1,3-butanediamine and 5.0 g of anhydrous magnesium sulfate were added to this, and the mixture was stirred at room temperature. Dispersed. After introducing oxygen from below the liquid surface for about 5 minutes, 15.8 g (0.06
4 mol) 2,6-diphenylphenol and 2.0 g
(0.016 mol) of 2,6-dimethylphenol was added and oxidative polymerization was carried out for about 5 hours. After the reaction was completed, the insoluble matter in the reaction solution was removed by filtration, reprecipitation from methanol was performed, and the operation of dissolving again in benzene and reprecipitating with methanol was repeated twice to purify and isolate the polymer. The yield after drying was 16.0 g and the weight average molecular weight was about 2.
It was 10,000. Further, this polymer was dissolved in deuterated chloroform, and the copolymerization composition ratio was calculated from the ratio of the number of protons of the phenyl group at the 2,6-position and the methyl group using 400 MHz- ¹ H-NMR to find that it was 80:20. It was found that a polymer having a composition ratio according to the charging ratio was obtained. The polymer thus obtained was dissolved in N-methylpyrrolidone to prepare a 16 wt% polymer dope, which was spin-coated on a silicon substrate at 3000 rpm for 30 seconds and then dried at 100 ° C. for 5 minutes and 200 ° C. for 5 minutes. As a result, a film having a uniform film quality and a film thickness of 1.1 μm with no surface irregularity under an optical microscope and visual observation was obtained. When the heat resistance of this coating was measured, it showed a high heat resistance with a 5% weight loss onset temperature of 490 ° C. Further, the dielectric constant at 1 MHz measured by forming an aluminum electrode on the coating was 2.7, which was a smaller value than 4.1 of the silicon dioxide film.

[0015]

[Embodiment 2] FIG. 1 shows a two-layer wiring structure using an insulating film obtained as in Embodiment 1 as a wiring interlayer insulating film. By the same method as in Example 1, a uniform insulating film having a film thickness of about 1 μm was formed on the first wiring conductor layer 3 formed of aluminum (Al) on the semiconductor substrate. next,
After forming a connection hole for electrically connecting to the second wiring conductor layer 6 by a dry etching technique, this connection hole is filled with tungsten (W) CVD, and a second wiring conductor layer of Al is formed on the connection hole. 6 could be formed by dry etching using sputtering and photolithography. Although the present embodiment describes the case of forming the two-layer wiring, the present invention is not limited to the two-layer wiring and can be used for forming the wiring of three or more layers.

[0016]

Comparative Example 1 Oxidative polymerization was carried out in the same manner as in Example 1 except that 2,6-diphenylphenol (0.008 mol) was not used and 2,6-dimethylphenol was not used. As a result, a polymer having a weight average molecular weight of about 30,000 was obtained. This was treated with N- by the same method as in Example 1.
After dissolving in methylpyrrolidone to prepare a 16 wt% polymer solution, spin coating was performed on a silicon substrate, but a uniform coating film was not obtained, and an insulating coating usable for a semiconductor device could not be formed.

[0017]

EFFECT OF THE INVENTION It is possible to provide an insulating coating having a low dielectric constant and a high heat resistance, and on which there are no problems due to fluorine atoms, such as adhesiveness and contamination of fluorine ions. Not only is it effective in solving problems such as signal delay and crosstalk of semiconductor devices, but it is also excellent in processability and reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a two-layer wiring structure using an insulating film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Silicon dioxide film 3 First wiring conductor layer made of aluminum 4 Insulating film 5 of the present invention 5 Tungsten plug 6 Second wiring conductor layer made of aluminum

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/95

Claims (4)

[Claims] 1. An insulating film made of a 2,6-diphenylphenol copolymer used for insulation between wiring layers of a semiconductor device having a multilayer wiring structure. 2. The 2,6-diphenylphenol copolymer is 50-98% by weight of 2,6-diphenylphenol.
And 50 to 2% by weight of a phenolic monomer copolymerizable with 2,6-diphenylphenol.
The insulating coating according to claim 1, which has a weight average molecular weight of 2000 or more and 500000 or less. 3. A polymer dope used for producing an insulating film according to claim 1, which comprises a 2,6-diphenylphenol copolymer and the solvent. 4. A semiconductor device having a multilayer wiring structure, wherein at least one layer of the wiring interlayer insulating coating of the semiconductor device is the insulating coating according to claim 1.