JPH01313942A - Semiconductor device - Google Patents

Abstract

PURPOSE:To form a multilayer interconnection in high reliability by a method wherein a double layer structured interlayer insulating film comprising a resin layer capable of flattening an underneath stepped part is used as a lower layer and another resin layer in excellent oxidation resistance as an upper layer. CONSTITUTION:An applicable interlayer insulating film is double layer structured, i.e. the lower layer insulating film comprises an organic silicon polymer capable of flattening an underneath stepped part while the upper layer insulating film comprises an aryl group containing organic silicon polymer with oxidation resistance. Such a double layer structured interlayer insulating film can flatten the surface of semiconductor substrate having rugged surface and can maintain the film quality thereof subject to no crack or release even if it is exposed to the oxygen atmosphere exceeding 400 deg.C or oxygen radical in high concentration or oxygen ionic atmosphere. Through these procedures, a multilayer interconnection of high reliability can be formed.

Description

[Detailed Description of the Invention] [Summary] Regarding a semiconductor device having a multilayer wiring structure, it is possible to flatten an uneven base, and to prevent cracks and damage caused by heat treatment in subsequent steps. The purpose of this invention is to provide an interlayer insulating film that has a two-layer structure, in which the lower insulating film is made of an organosilicon polymer that can flatten the underlying step, and the upper insulating film is The film is made of an aryl group-containing organosilicon polymer that has oxidation resistance.

[Industrial application field]

The present invention relates to a semiconductor device, and more specifically, to a semiconductor device having a multilayer wiring structure.

In other words, the present invention relates to a method for forming multilayer interconnections for semiconductor integrated circuits, and more specifically, when forming multilayer interconnections for semiconductors with high integration density such as ICs and LSIs, the present invention provides excellent insulation while flattening the underlying steps. The present invention relates to a highly reliable multilayer wiring formation method by providing an interlayer insulating film having the following characteristics.

[Conventional technology]

BACKGROUND ART In semiconductor integrated circuits, as the degree of integration has improved, there has been a demand for three-dimensional wiring for the purpose of facilitating wiring and improving operating speed, and multilayer wiring has therefore been developed.

When forming multilayer wiring, after applying the first layer wiring,
It has been common practice to provide a second layer of wiring via an insulating film and repeat this process in sequence.

Here, the materials used for the interlayer insulating film are conventionally
Inorganic films such as silicon dioxide, silicon nitride, and phosphorous glass (PSG) are formed by CVD vapor phase growth using silane-based gases, or polymer insulating materials such as polyimide and silicone resin, or Although these laminates have been used, materials with better characteristics in terms of reliability have been required as wiring patterns become finer.

When considering multilayer wiring, the semiconductor substrate with the first layer wiring has unevenness due to the wiring, so if you use this as a base and form an inorganic film on top of it, the surface of the interlayer insulating film will reproduce the unevenness of the base as it is. Put it away. This causes disconnection, poor insulation, etc. of the upper layer wiring formed thereon. Therefore, the development of interlayer insulating materials that can flatten the substrate surface when applied to an uneven substrate, and methods for obtaining a flat surface from an insulating film manufacturing process such as etch-back method and bias sputtering method, and resin A method of forming a flat insulating film using a spin code method is being considered.

Among these methods, the resin coating method is a simple process in which a resin is applied and then heated and cured to form a film. Conventional resin materials used here include polyimide, spin-on glass, and the like. However, carbon-based materials such as polyimide have drawbacks such as a low etching selectivity with existing resist in the subsequent resist stripping process, and spin-on glass has the disadvantage that when coated thickly, condensation occurs during curing. Cracks are likely to occur due to distortion.

Therefore, many silicone resins have been developed for interlayer insulation films.

Above all, a ladder-type silicone resin represented by polymethylsilsesquioxane is a material that has excellent ability to flatten base steps and does not cause cracks up to a film thickness of about 3 pm in an inert gas atmosphere.

[Problem to be solved by the invention]

In the multilayer wiring process of semiconductor devices, in many cases, after coating the silicone resin as described above, the heating temperature is 400°C.
It is essential to be exposed to the above oxygen atmosphere, or to a high concentration oxygen radical or oxygen ion atmosphere. Therefore,
Interlayer insulating films are required to have excellent oxidation resistance. However, the polymethylsilsesquioxane described above is heated at 400°C.
In the above oxygen atmosphere, cracks are likely to occur due to oxidative deterioration.

On the other hand, organosilicon resins having an aryl group in the molecule, such as polyphenylsilsesquioxane and polydimethylsilphenylene disiloxane, are also known. These resins have an improved oxidation temperature and are less likely to be oxidized in an oxygen atmosphere of about 400°C. However, in the case of such resins, the film strength tends to decrease, and when used alone as an insulating film between the eyebrows, cracks are likely to occur due to stress caused by thermal expansion of wiring materials such as aluminum (Aj'). It is difficult to thicken the film.

The purpose of the present invention is to eliminate these drawbacks, and provide an interlayer insulating film that can flatten an uneven base and does not cause cracks and damage due to heat treatment in subsequent steps. The purpose is to

[Means to solve the problem]

According to the present invention, the glabellar insulating film included has a two-layer structure, the lower insulating film is made of an organosilicon polymer capable of flattening the underlying step, and the upper insulating film This can be achieved by a semiconductor device with a multilayer wiring structure made of an aryl group-containing organosilicon polymer that has oxidation resistance.

In the semiconductor device of the present invention, the lower layer of the two-layer interlayer insulating film is made of an organosilicon polymer capable of flattening the underlying step, as described above. In the first place, the resin used for the lower of the two layers is designed to flatten unevenness caused by wiring, etc., and to withstand stress caused by thermal expansion of the base material during heating, creating a film that does not crack or peel. Any material may be used as long as it can be formed, but organosilicon polymers are preferred in view of compatibility with subsequent steps.

More specifically, the organosilicon polymer useful as the lower insulating film is a polymer compound having a polyorganosilsesquioxane as a structural unit represented by the following general formula (1): CL 5tO3z2]n
...(I) (In the above formula, RI is hydrogen, a hydroxyl group, such as a methyl group, an ethyl group, n-
represents an alkyl group such as propyl group, i-propyl group, or an alkoxy group such as methoxy group, ethoxy group, n-propoxy group, i-propoxy group, and n is 10 to
50.000). The structural formula of the polyorganosilsesquioxane represented by the general formula (I) is as follows: (R1 in the formula may be the same or different and is the same as the above definition, and n is the same as defined above)
.

Another example of an organosilicon polymer useful as a lower insulating film is a polymer compound having polydiorganosylalkylene disiloxane as a structural unit represented by the following general formula (n): (R+StO□/ 2(R2)l
/2) -...(Il) (In the above formula, R1 is the same as defined above, and is hydrogen, a hydroxyl group, for example, a lower alkyl group such as a methyl group, an ethyl group, an n-propyl group, a 1-propyl group, etc.) or a lower alkoxy group such as a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, R2 represents an alkylene group such as a methylene group or an ethylene group, and n is 10 to 50.0.
(represents an integer of 00). Here, Ro and R2 in the formula are
It may be replaced as necessary.

The organosilicon polymer of the general formula (n) above preferably has:
It is a polymer of the following structural formula (b) or (C) or a mixture of these polymers.

(R, , R, and n in the formula are each the same as defined above).

In the semiconductor device of the present invention, the upper insulating film is made of an aryl group-containing organosilicon polymer that has oxidation resistance. Here, the inclusion of an aryl group in the molecule of the organosilicon polymer is an essential condition for ensuring satisfactory oxidation resistance.

Note that the resin used for the upper layer of the two layers is heated to 400°C.
Any material may be used as long as it can form a film that is resistant to oxidation and does not cause cracks or peeling even in the above oxygen atmospheres or in high-concentration oxygen radical or oxygen ion atmospheres, but in consideration of compatibility with subsequent processes, organic Silicon polymers are preferred.

More specifically, the organosilicon polymer useful as the upper insulating film is a polymer compound having a polyorganosilsesquioxane represented by the following general formula (n) as a structural unit.

[R, -3in, □]. ...(III)
(In the above formula, R8 represents an aryl group such as a phenyl group, tolyl group, or naphthyl group, and n is 10
~50.000). This general formula (III
) The structural formula of the polyorganosilsesquioxane represented by
(n is the same as defined above).

Another example of an organosilicon polymer useful as an upper insulating film is a polymer compound having a polydiorganosylarylene disiloxane as a structural unit represented by the following general formula (rV): [R,5in2 ．． □(R4)
I/□]7...(IV) (In the above formula, R1
is the same as the above definition, hydrogen, hydroxyl group,
It represents a lower alkyl group or a lower alkoxy group, R1 represents an arylene group such as a 0-+m- or p-phenylene group, tolylene group, or naphthylene group, and n represents an integer of 10 to 50.000. ). Here, R1 and R1 in the formula may be substituted as necessary.

The organosilicon polymer represented by the above general formula (rV) is preferably a polymer represented by the following structural formula (e) or (f), or a mixture of these polymers.

(R+, R4 and n in the formula are each the same as defined above).

In carrying out the present invention, both the upper and lower layers of the interlayer insulating film having a two-layer structure can be formed by any method. However, it is particularly recommended to use the spin coating method because it is a simple process and is advantageous for flattening the underlying layer.

The thicknesses of the upper insulating film and the lower insulating film can be varied within a wide range. However, the upper insulating film should be as thin as possible as long as it does not allow oxygen to pass through, and is generally preferably from 0.1 to 0.57. On the other hand, the thickness of the lower insulating film is generally preferably 1 to 2 Ja in consideration of planarization of the underlying layer.

Moreover, any combination of the upper layer and lower layer of the insulating film may be used as long as the adhesion of each layer is good. In addition, the interlayer insulating film having this two-layer structure can be used alone as an interlayer insulating film, or in combination with an inorganic film such as silicon dioxide, silicon nitride, or phosphorous glass (PSG) to form an interlayer insulating film. Either may be used as an insulating film.

[For production]

The interlayer insulating film having a two-layer structure according to the present invention can flatten the surface of a semiconductor substrate having an uneven surface, and
Even when exposed to an oxygen atmosphere at temperatures above ℃ or a high concentration of oxygen radicals or oxygen ions, it does not crack or peel, and can maintain its film quality. Therefore, it can be expected to have sufficient insulation properties and is suitable for use as an interlayer insulating film for semiconductor integrated circuits.

〔Example〕

The present invention will be explained below with reference to Examples.

Example 1 (Preparation example) 1. Dissolve 5 g of 2-bis(methyldichlorosilyl)ethane in 50 cc of tetrahydrofuran, 100 cc of methyl isobutyl ketone, and 50 c of methyl cellosolve acetate.
c, triethylamine 15cc and ion exchange water 30c
It was added dropwise to the mixed system of c and stirred at 75°C for 3 hours. After cooling, the mixture was allowed to stand to remove the aqueous layer, and then thoroughly washed with water.

The resulting reaction solution was dried and the remaining resin was dissolved again in 1,4-dioxane and freeze-dried. 2.8g of polydimethylsilethylenedisiloxane powder was recovered.

Example 2 The powder obtained in Example 1 was dissolved in isoamyl acetate, a semiconductor element was formed, and a first layer of aluminum wiring was applied on a silicon substrate (thickness of aluminum is 1-1, minimum line width is 1-1, minimum line width is 1-1). The interval is 1.57-) to 1.04191. spin coated on. After coating, the solvent was dried at 80°C for 20 minutes, followed by drying in nitrogen.
Heat treatment was performed at 420°C for 1 hour. The level difference on the substrate surface after the heat treatment was approximately 0.2Isa, and the level difference caused by the aluminum wiring had been flattened. Subsequently, polydimethyl-p-silphenylene disiloxane powder subjected to terminal trimethylsilylation was dissolved in isoamyl acetate and applied to a thickness of 0.7 μm on the film formed by the above method. After application, solvent drying at 80°C for 20 minutes, followed by drying at 420°C in air.
, 15 m1n of heat treatment was performed. No cracks, peeling, etc. were observed in the coated film after treatment. Next, through holes are formed and a second layer of aluminum wiring is formed, and a protective layer of 1.2
After forming a - SiO□ film, a window for taking out an electrode was opened to obtain a semiconductor device. This device operates at 420℃ in the atmosphere.
No defects were observed even after a 1-hour heating test at 100°C and 10 thermal shock tests from -65°C to 150°C.

Example 3 After forming a two-layer structure film in the same manner as in Example 2, a PSG film was further formed using a 0.3p normal pressure CVD method. This film flattened the underlying level difference to about 0.2 pm. Thereafter, a semiconductor device was manufactured and tested in the same manner as in Example 2, and no defects were found.

Comparative Example 1 After forming the lower layer polydimethylsilethylene disiloxane film in the same manner as in Example 2, it was heated at 420°C in the atmosphere.
A heat treatment of 15 ml was performed. Severe cracks appeared on the entire surface of the film after the treatment, and it was no longer possible to manufacture a semiconductor device thereafter.

Comparative Example 2 In the same manner as in Example 2, the lower polydimethylsilethylene disiloxane film was coated with 1. After forming Ojs, 420℃ in nitrogen
, heat treatment was performed for 1 hour. After that, when a PSG film was formed using the 0.3mm atmospheric pressure CVD method, cracks appeared on the entire surface of the film.
It was not possible to manufacture semiconductor devices thereafter.

〔Effect of the invention〕

The present invention is an interlayer insulating film used in the process of forming multilayer wiring for semiconductor integrated circuits, which has a two-layer structure in which a resin layer for flattening the underlying step is used as a lower layer, and a resin layer with excellent oxidation resistance is used as an upper layer. It is characterized by using a membrane. According to the present invention, by using the interlayer insulating film described above, it is possible to completely flatten the high level difference that occurs in the wiring process, and it is also possible to completely flatten the high-level difference that occurs in the wiring process, and it is also possible to completely flatten the high-level difference that occurs in the wiring process. can prevent cracking and peeling.

Therefore, it is possible to form highly reliable multilayer wiring without causing wire breakage or insulation failure.

Claims (1)

[Claims] 1. The interlayer insulating film included has a two-layer structure, the lower insulating film is made of an organosilicon polymer that can flatten the underlying step, and the upper insulating film has oxidation resistance. A semiconductor device with a multilayer wiring structure made of an aryl group-containing organosilicon polymer.