JPH05156021A - Organic silicon polymer and production of semiconductor device - Google Patents

Abstract

PURPOSE:To provide an interlaminar insulating film using an organic silicon polymer, excellent in the heat resistance and flatness and free from the generation of cracks. CONSTITUTION:An organic silicon polymer of formula I (RA is lower fluoroalkyl; (n) is 10-50000) having a weight-average mol.wt. of 1000-5000000, or an organic silicon polymer produced by substituting a part of the hydrogen atoms of silanol groups contained in the organic silicon polymer of formula I with triorganosilyl groups of formula II (RB is lower fluoroalkyl or aryl) is employed to form the interlaminar insulating film of a semiconductor integrated circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic silicon polymer and a method for forming an interlayer insulating film of a semiconductor integrated circuit using the same.

Since it is necessary to process a large amount of information at a high speed, the semiconductor devices forming the main body of an information processing apparatus have been highly integrated, and LSI and VLSI have been put into practical use, and further, ULSI has been put into practical use. ..

Here, the integration is performed by miniaturization of the unit element which constitutes the element rather than by increasing the size of the chip, and the minimum line width of the wiring has reached sub-micron. Also, the electronic circuit has a multilayer structure with an interlayer insulating film interposed.

Therefore, it is necessary that the material for forming the interlayer insulating film is excellent in heat resistance and flatness of the underlayer and has a low dielectric constant.

[0005]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, a large number of electrodes, wirings, etc. are multilayered on a semiconductor substrate. The presence of this step significantly lowers the reliability of the multilayer wiring.

For this reason, the interlayer insulating film is required to have excellent flattening property in addition to excellent electrical insulation and heat resistance. Here, inorganic and organic insulators are used as the material for forming the interlayer insulating film.

That is, as the inorganic insulating material, silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), phosphosilicate glass (abbreviated as PSG) is used.
The film is formed on the substrate to be processed by a vapor phase growth method (CVD method) or the like.

However, although these insulating films have excellent characteristics such as electrical characteristics and heat resistance, they do not meet the purpose of flattening in order to faithfully reproduce the irregularities of the underlying substrate during formation.

Therefore, an inorganic insulating film is formed by a CVD method or the like, and then an organic insulating material is applied to planarize it, and then dry etching is performed until the inorganic insulating film appears to obtain a flat surface. It is proposed to use the bias sputtering method to form a flat surface by forming an inorganic insulating film and sputtering at the same time while scraping the convex portion, but it requires a lot of man-hours and time, so it is practical. Not a method.

On the other hand, as the organic insulator, there are polyimide resin and silicon resin, and the coating liquid obtained by dissolving this in a solvent can form a film on the substrate by the spin coating method, and therefore has excellent flatness. But there are some problems.

That is, the polyimide resin is decomposed at about 450 ° C., has a high hygroscopic property, and has a drawback that it contains corrosive impurities such as alkali metals. Further, the silicon resin has a drawback that it is easily oxidized at a temperature of about 400.degree. C. or thermally decomposed at a temperature of 500.degree.

The insulating material must have a small dielectric constant (ε). In other words, what is required when a multilayer wiring structure is adopted is to reduce cross-talk between layers and to reduce the delay time (τ) of electric signals, and for that purpose, the dielectric constant (ε) It is necessary to use a small insulating material.

Here, the delay time (τ) of the electric signal is τ = ε ^1/2 / c (3) where c is the speed of light.

For these reasons, it is desired to develop an organic insulating material having a low dielectric constant, excellent heat resistance, high purity and low hygroscopicity.

[0015]

When forming an integrated circuit such as VLSI or ULSI that requires multi-layer wiring, an interlayer insulating film having a small dielectric constant, excellent heat resistance, and excellent planarization of the substrate is required. ..

Therefore, this development is an issue.

[0017]

[Means for Solving the Problems]
An organic silicon polymer having a weight average molecular weight of 1000 to 5,000,000 represented by (1) is used, or a part of hydrogen atoms of a silanol group contained in the organic silicon polymer is replaced by the following general formula (2). The problem can be solved by forming an interlayer insulating film of a semiconductor integrated circuit using an organic silicon polymer substituted with a triorganosilyl group represented by

( ^RA SiO _1.5 ) _n ... (1) where ^RA is a lower fluoroalkyl group and n is 10 to 50,000.
Integer _{^{(R B) 3 Si- ········ (}} 2) where, R ^B is a lower fluoroalkyl group or an aryl group,

[0019]

The present inventors have introduced a fluorine atom into an organic silicon polymer as a method for satisfying the above requirements.

That is, the fluororesin is excellent in heat resistance, electric insulation and chemical resistance as compared with other resins as represented by polytetrafluoroethylene (trade name Teflon), and has a dielectric constant (ε). It has the characteristic of being small.

Therefore, as shown by the general formula (1), a lower fluoroalkyl group is used in place of the alkyl group of the organic silicon polymer having a ladder type siloxane structure, or silanol at the end of the organic silicon polymer is further used. By substituting a part of hydrogen (H) atoms of the group with a triorganosilyl group represented by the general formula (2), the low dielectric constant and the heat resistance are improved.

Structural formula (4) is a modification of the above formula (1) for easy understanding, and structural formula (5) is the above formula.
The case where two lower fluoroalkyl groups related to formula (2) are substituted is illustrated.

Here, as the lower fluoroalkyl group,
-CF ₃ , -C ₂ F ₅ etc. are applicable.

[0024]

[Chemical 1]

[0025]

[Chemical 2] The polyorganosilsesquioxane resin according to the present invention is soluble in many organic solvents and can be formed into a film on a substrate to be processed by spin coating as in the case of conventional organic silicon polymers.

Therefore, it is possible to easily achieve the flattening of the substrate surface with a step, and it is possible to improve the electric signal transmission characteristic because the dielectric constant is lower than that of the conventional resin.

[0027]

【Example】

Synthesis Example 1 (related to claim 1) To a four-necked flask having a capacity of 300 cc, 100 cc of methyl isobutyl ketone, 15 cc of triethylamine as a catalyst and 10 g of fluoromethyltrichlorosilane were added, and the mixture was cooled to −60 ° C. while continuing stirring. did.

Next, 30 cc of pure water was added to this four-necked flask.
It dripped over minutes. After the dropping is completed, the reaction system is heated to 2.0 ° C.
The temperature was raised at a rate of / min, the temperature was maintained at 80 ° C, and stirring was continued for 2 hours.

After the reaction was completed and the mixture was cooled to room temperature, it was washed with a large amount of water. The washed reaction solution was concentrated using an evaporator, the precipitate was collected with acetonitrile, and freeze-dried to obtain white powder A. Synthetic Example 2: (Related to Claim 2) The polymer obtained in Synthetic Example 1 was again dissolved in methyl isobutyl ketone, 20 cc of pyridine was added as a catalyst, the mixture was heated to 60 ° C, and phenyldi (trifluoromethyl) chlorosilane was added to 20 cc. After the addition, the reaction was carried out at this temperature for 3 hours, and the hydrogen atoms of the unreacted hydroxyl groups were replaced with vinyldimethylsilyl groups.

After the reaction was completed, the reaction solution was poured into a large amount of acetonitrile to precipitate and collect the resin, which was freeze-dried to obtain a white powder B. Example 1 (related to claim 3) The white powder A obtained in Synthesis Example 1 was dissolved in methyl isobutyl ketone to prepare a 20% by weight resin solution.

A semiconductor element is formed, and the resin solution is applied to the Si substrate on which the first-layer polysilicon wiring is formed by applying 3000 parts of this resin solution.
Spin coating was performed under the conditions of rpm and 45 seconds. The thickness of the polysilicon wiring is 1 mm, the minimum line width is 1 μm, and the minimum line interval is 1.5 μm.

After coating, the resin solution is dried at 80 ° C. for 20 minutes,
Further, heat treatment was performed at 450 ° C. for 30 minutes. The step difference on the substrate surface after the heat treatment was about 0.2 μm, and the step difference caused by the wiring was flattened.

Next, a through hole is formed in this insulating film, a wiring of polysilicon is formed thereon, and a PSG film having a thickness of 1 μm is formed as a protective layer by the atmospheric pressure CVD method.
A semiconductor device could be obtained by opening a window for taking out an electrode.

In this semiconductor device, the signal propagation speed was increased by about 30% as compared with the conventional device using a PSG film as an insulating film. In addition, a heating test at 450 ° C for 1 hour in air and
No defects were found at all even after 10 thermal cycle tests at 65 ° C to + 150 ° C. Example 2: (Related to Claim 3) The white powder B obtained in Synthesis Example 2 was dissolved in methyl isobutyl ketone to prepare a 20 wt% resin solution.

This resin solution was spin-coated under the condition of 3000 rpm for 45 seconds on a Si substrate on which a semiconductor element was formed and on which Al wiring of the first layer was formed. The thickness of the Al wiring is 1 mm,
The minimum line width was 1 μm and the minimum line spacing was 1.5 μm.

The resin solution is dried at 80 ° C. for 20 minutes after coating,
Further, heat treatment was performed at 450 ° C. for 30 minutes. The step difference on the substrate surface after the heat treatment was about 0.2 μm, and the step difference caused by the wiring was flattened.

Next, a through hole is formed in this insulating film, and Al wiring is formed on the through hole, and the thickness of the protective layer is 1 μm.
After forming a PSG film of m 2 by the atmospheric pressure CVD method, a window for taking out an electrode was opened to obtain a semiconductor device.

In this semiconductor device, the signal propagation speed was increased by about 30% as compared with the conventional device using a PSG film as an insulating film. In addition, the occurrence of cracks on Al wiring, which was observed when using a conventional organic silicon polymer, was not found.

[0039]

According to the present invention, an interlayer insulating film having a lower dielectric constant than other organic insulating materials, excellent heat resistance and flatness, and free from cracks can be obtained. The characteristics and reliability of can be improved.

Claims (3)

[Claims] 1. An organic silicon polymer represented by the following general formula and having a weight average molecular weight of 1000 to 5,000,000. ( ^RA SiO _1.5 ) _n ... (1) However, ^RA is a lower fluoroalkyl group, and n is an integer of 10 to 50,000. 2. A part of the hydrogen atom of the silanol group contained in the organic silicon polymer represented by the formula (1) is replaced by the following general formula:
An organosilicon polymer characterized by being substituted with a triorganosilyl group represented by (2). _{^{(R B) 3 Si- ········ (}} 2) where, R ^B is a lower fluoroalkyl group or an aryl group, 3. A method of manufacturing a semiconductor device, comprising forming an interlayer insulating film of a semiconductor integrated circuit by using the organic silicon polymer according to claim 1.