JPH0822986A - Method for forming insulating film - Google Patents

Abstract

(57) [Summary] [Structure] Using a source gas containing an organic Si compound having a Si-N bond, a lower layer insulating film composed of a SiN-based thin film having a relatively high hydrocarbon group content is formed on a substrate by plasma CV.
After the film formation by D, the mixed gas containing SiH ₄ and N ₂ or NH ₃ is used while the substrate is kept in the state of being shielded from the atmosphere, or the organic Si having the Si—N bond is used.
Using the compound and N ₂ or NH ₃ , an upper insulating film made of a SiN-based thin film having a relatively low hydrocarbon group content is formed on the lower insulating film by plasma CVD. [Effect] While ensuring excellent coverage, insulation resistance,
An insulating film having excellent film quality such as water resistance and corrosion resistance can be formed. Therefore, it is possible to improve the performance and yield of semiconductor devices based on fine design rules. Moreover, it does not reduce the throughput and is economically efficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an insulating film used as a final protective film of a wafer or an interlayer insulating film in a semiconductor device, and particularly to a SiN film formed by using an organic Si compound as a source gas. System insulation film and Si
The present invention relates to a method for improving insulation resistance and water resistance of an ON-based insulating film.

[0002]

2. Description of the Related Art Conventionally, a SiN-based insulating film has been widely used as a final protective film of a wafer, that is, a so-called passivation film. When forming the SiN-based insulating film, the film is formed at a low temperature by the plasma CVD method so as not to damage the already-formed low-melting-point material layer such as the Al-based wiring. As a raw material gas, conventionally, S
An iH ₄ / NH ₃ mixed gas, a SiH ₄ / N ₂ mixed gas, etc. have been used.

However, the SiN film thus formed
The coverage of the system insulating film cannot follow the increase in the surface step of the substrate due to the miniaturization of the semiconductor device or the multi-layer wiring. FIG. 4 shows a wafer in which the SiO-based interlayer insulating film 2 and the Al-based wiring 3 are formed on the Si substrate 1 and the SiN-based insulating film 14 is formed thereon. The void 15 has been formed due to the poor differential coverage. Also, cracks are likely to occur in such a SiN-based insulating film 14.

As a method for improving the above step coverage, it has been proposed to control the plasma state by the dual frequency method. This is because, in a parallel plate electrode of a plasma CVD apparatus, a low frequency RF voltage of several hundred kHz is applied to the electrode on the side where the wafer is placed, and MHz is applied to the other electrodes.
A high-frequency RF voltage of the order is applied, and an attempt is made to increase low-energy ion bombardment and improve coverage. However, even with this method, it is not possible to sufficiently cope with the miniaturization of the pattern and the increase of the surface gap, and the conformal film formation has not been achieved yet.

Therefore, SiN which is more excellent in coverage
As a method of forming a system insulating film, it has been proposed to perform CVD using an organic Si compound as a source gas. here,
The organic Si compound means [(CH ₃ ) ₂ N] ₄ Si,
[(CH ₃ ) ₂ N] ₃ SiH, [(CH ₃ ) ₂ N] ₂ S
It is a compound such as iH _{2 which has} Si atoms, N atoms, C atoms and H atoms as main constituent elements and has a Si—N bond. When a film is formed using this as a raw material gas, the SiN bond can be formed efficiently due to the presence of the Si—N bond. In addition, since the hydrocarbon group is cleaved from the organic Si compound during the film formation, the intermediate product that retains the Si—N bond is easily polymerized, and the fluidity becomes high. It is believed that a system insulating film can be formed.

[0006]

However, in the SiN type insulating film formed by using the organic Si compound as described above, the insulation resistance is deteriorated due to the residual hydrocarbon groups, and the water resistance and the corrosion resistance are deteriorated. There is concern that the property may deteriorate.

Therefore, the present invention has been proposed in view of such conventional circumstances, and an object thereof is to provide a method for forming an insulating film which does not deteriorate the film quality while ensuring excellent coverage.

[0008]

The method for forming an insulating film according to the present invention has been proposed in order to achieve the above-mentioned object, and a source gas containing an organic Si compound having a Si--N bond is used. Using SiN thin film or SiON on the substrate
Of a lower insulating film composed of a system-based thin film having a relatively high hydrocarbon group content by CVD, and an upper layer composed of a SiN-based thin film having a relatively low hydrocarbon group content on the lower-layer insulation film And a step of forming an insulating film by CVD.

As the source gas introduced for forming the lower insulating film, an organic Si compound having a Si--N bond is used in order to efficiently obtain a desired reaction product. , Azido group (hereinafter referred to as —N ₃ group) and —NR ₂ (wherein R is a hydrocarbon group having 1 or more carbon atoms) group can be used. In particular, when —NR ₂ is bonded to the Si atom, the hydrocarbon group is cleaved during film formation, the intermediate product produced is easily polymerized, and the fluidity is increased, thus improving the coverage. Is also connected.

Furthermore, when an alkyl group (hereinafter referred to as -R 'group) and / or an alkoxyl group (hereinafter referred to as -OR''group) is bonded to the above Si atom, these are formed at the time of film formation. Cleavage of the —R ′ group and the —OR ″ group increases the fluidity of the intermediate product that is formed, and improves the coverage of the lower insulating film.

The H atom directly bonded to the Si atom is
Unlike the above-mentioned —NR ₂ group, —N ₃ group, —R ′ group, and —OR ″ group, it does not exhibit the effect of maintaining the Si—N bond to improve the film formation efficiency and the effect of improving the coverage. So
It is better not to bond even one Si atom, or to make a small number even if bonded.

Furthermore, an organic Si compound having a Si--Si bond may be used in order to improve the film formation rate of the lower insulating film. This makes it possible to increase the flow rate of the source gas supplied during film formation and to increase the film formation rate without increasing the power applied to the electrodes of the plasma CVD apparatus, thus increasing the uptake of impurities, Throughput can be improved without causing a problem such as deterioration of coverage.

Therefore, among the organic Si compounds used for forming the lower insulating film, those having the most desirable structure can be represented by the following general formula (1).

Si _n (NR ₂ ) _w (N ₃ ) _x (R ′) _y (OR ″) _z ... (1) (where w, x, y, and z are w + x + y + z = 2n +
2, 0 ≦ w ≦ 2n + 2, 0 ≦ x ≦ 2n + 2, 1 ≦ w + x
An integer satisfying ≦ 2n + 2, 0 ≦ y ≦ 2n + 1, 0 ≦ z ≦ 2n + 1, and n is an integer of 1 or more. Also, R '
And R ″ represent an aliphatic saturated hydrocarbon group having 1 or more carbon atoms, and R represents a hydrocarbon group having 1 or more carbon atoms. The carbon skeleton of the hydrocarbon group represented by R, R ′ and R ″ is not particularly limited, and may be saturated hydrocarbon or unsaturated hydrocarbon. In each case, a linear, branched, or cyclic carbon skeleton is conceivable, but any of these may be used, and examples thereof include a methyl group, an ethyl group, and a cyclopentadienyl group. .

In the above general formula (1), when z = 0, that is, when the organic Si compound is one in which the --OR '' group is not bonded, this is used as a source gas, and an oxygen-based gas is added to this. If they are not mixed, a SiN-based thin film will be formed. On the other hand, when x ≧ 1, that is, when the compound is an organic Si compound having an —OR ″ group bonded, when this is used as a source gas, a trace amount of O atoms is taken in during film formation, so that an oxygen-based gas is used. The SiON-based thin film can be formed without using the above.

In the method of forming an insulating film according to the present invention, SiN is formed on the lower insulating film made of the SiN thin film or the SiON thin film formed as described above.
An upper insulating film having a relatively low content of hydrocarbon groups is formed from a system thin film. That is, the upper insulating film is formed as a film having high insulation resistance, water resistance and corrosion resistance.

A mixed gas containing an inorganic Si compound and a compound containing N ₂ and / or N atoms is preferably used as a source gas for forming the upper insulating film made of a SiN-based thin film. This makes it possible to form a SiN-based thin film in which hydrocarbon groups are not incorporated, and becomes an upper insulating film having excellent insulation resistance, water resistance, and corrosion resistance. Since this upper insulating film is formed on the lower insulating film which covers the surface steps of the substrate with good step coverage and is flattened to some extent, there is no concern about step coverage.

SiH ₄ is typically used as the inorganic Si compound, and NH 3 is used as the compound containing the N atom.
₃ is typical.

Further, as a raw material gas for forming an upper insulating film made of a SiN-based thin film, an organic Si compound and N _{2 are used.}
And / or a compound containing an N atom may be used.
Since the compound containing N ₂ or N atom acts as a reducing agent for the hydrocarbon group, when used in combination with the organic Si compound, the hydrocarbon group is withdrawn before the intermediate product produced is polymerized, or The hydrocarbon group taken into the formed SiN-based thin film is extracted to form an upper insulating film in which the content of the hydrocarbon group is suppressed. The upper insulating film is excellent in coverage, though the hydrocarbon group is removed to some extent before the intermediate product is polymerized.

Furthermore, if a plasma treatment is carried out by introducing a compound containing N ₂ and / or N atoms into the reaction chamber not only during film formation but also as a post-treatment after film formation, the surface layer portion of the upper insulating film can be treated. The hydrocarbon group can be further reduced.
If the SiN-based thin film is formed to a desired film thickness by alternately repeating the film formation and the above-described post-treatment a plurality of times, the content of hydrocarbon groups is sufficiently reduced not only in the surface layer portion but also in the deep layer portion. Since the formed upper insulating film can be formed, it is not always necessary to mix the compound containing N ₂ and / or N atom with the organic Si compound. When the compound containing N ₂ and / or N atom is not mixed with the organic Si compound, it does not hinder the polymerization of the intermediate product at the time of film formation, so that the upper insulating film having excellent coverage can be obtained. .

The organic Si compound used for forming the upper insulating film is preferably one having a Si--N bond, and the same organic Si compound used for forming the lower insulating film can be used. Is. However, in general, SiON
Since the system-based thin film is inferior in insulation resistance and water resistance to the SiN-based thin film, it is better not to use an organic Si compound containing no O atom or to use oxygen gas together. In addition,
NH ₃ is a typical example of a compound containing an N atom, but hydrogen azide (N ₃ H), ammonia derivative, hydrazine (N ₂ H ₄ ), hydrazine derivative, methylhydrazine, etc. Those containing H atoms can be used.

Since the upper insulating film made of the SiN thin film obtained as described above has high insulation resistance, high water resistance and corrosion resistance, even if hydrocarbon groups remain in the lower insulating film, The insulation resistance, water resistance, and corrosion resistance of the entire insulating film can be sufficiently secured. That is, in the lower insulating film, it is not required to reduce the content of the hydrocarbon group, so that it is possible to further improve the step coverage. Needless to say, even when the lower insulating film is formed, a small amount of N is added to the organic Si compound as long as the coverage is not deteriorated.
H ₃ and N ₂ may be mixed to reduce the content of hydrocarbon groups.

In forming the lower insulating film and the upper insulating film as described above, in order to prevent deterioration of the quality of the lower insulating film, the substrate is removed from the atmosphere after the lower insulating film is formed. It is preferable to form the upper insulating film while maintaining the cutoff state. To do this, the substrate is moved from the reaction chamber for forming the lower insulating film to the reaction chamber for forming the upper insulating film in a so-called multi-chamber type apparatus having a common vacuum transfer path with a plurality of reaction chambers. The lower layer insulating film and the upper layer insulating film may be continuously formed while the substrate is placed in the same reaction chamber in order not to reduce the throughput.

By the way, at the time of forming the lower insulating film and the upper insulating film as described above, since it is possible to perform processing at a low temperature so as not to damage the Al-based wiring, plasma is generated in the reaction chamber. However, it is suitable to form a film. Note that it is necessary to optimize the plasma CVD conditions for forming the lower insulating film and forming the upper insulating film. The plasma CVD apparatus used may be a parallel plate plasma CVD apparatus or a magnetic field microwave plasma CVD apparatus capable of generating high density plasma under low pressure.

During film formation by plasma CVD, intermediate products, by-products, undissociated components of raw material gas, and the like are present near the substrate surface in addition to the desired insulating film components, and these impurity components are easily incorporated. Further, in plasma CVD using SiH ₄ , it has been reported that particles are generated by plasma and these particles are taken into the film, and similar problems occur even when an organic Si compound is used. Is also concerned. Therefore, it is preferable from the viewpoint of improving the film quality to intermittently generate the plasma and prevent the chemical species other than the desired chemical species from accumulating on the substrate surface.

When plasma is generated intermittently,
It is easy to maintain the optimum plasma discharge conditions by optimizing the plasma generation time and the plasma stop time and the duty ratio, so it is possible to generate a desired chemical species from the organic Si compound. It is possible to control the conditions.

In order to generate the plasma intermittently, when a parallel plate type plasma CVD apparatus is used, RF
The generation and extinction of plasma may be repeated by turning on / off the current supply to the electrodes. Further, in the case of using the magnetic field microwave plasma CVD apparatus, even if the power supply to the magnetron, which is a microwave generation source, is turned on / off, or the power supply to the magnetron is turned on / off, On / off of power supply to the solenoid coil, which is the source of the magnetic field, may be synchronized.

[0028]

The insulating film formed by applying the present invention is excellent in step coverage and has high insulation resistance, water resistance and corrosion resistance. This is for the following reasons.

When film formation is performed using a source gas containing an organic Si compound to improve coverage, hydrocarbon groups are incorporated into the film, resulting in deterioration of insulation resistance, water resistance and corrosion resistance. However, when the present invention is applied to cover such a thin film (lower insulating film) with a thin film having a relatively low hydrocarbon group content (upper insulating film), high insulation resistance, water resistance, and Corrosion can be secured.

Further, a thin film having a low hydrocarbon group content tends to be inferior in coverage, but in the present invention, the upper insulating film requiring a low hydrocarbon group content is a lower layer formed with good coverage. Since the film is formed on the insulating film and the surface of the lower insulating film is flattened to some extent, poor coverage does not pose a problem.

Therefore, it is possible to secure a high step coverage in the lower insulating film and a high insulation resistance, water resistance and corrosion resistance in the upper insulating film.

In particular, the upper insulating film is composed of an inorganic Si compound and N.
_When a film is formed using a mixed gas containing ₂ and / or a compound containing an N atom, hydrocarbon groups are not incorporated into the upper insulating film, so that extremely high insulation resistance, water resistance, and corrosion resistance can be secured. .

On the other hand, the upper insulating film is formed of an organic Si compound and N.
_When a film containing a compound containing ₂ and / or N atoms is used, the compound containing N ₂ and / or N atoms functions to pull out a hydrocarbon group, and high insulation resistance, water resistance, and corrosion resistance can be secured. . Also, a relatively high step coverage can be secured.

By the way, after forming the lower layer insulating film, if the upper layer insulating film is formed while being kept in a state of being shielded from the atmosphere, deterioration of the quality of the lower layer insulating film can be prevented. That is, while the lower insulating film has excellent step coverage, it is worried about water resistance due to its relatively high content of hydrocarbon groups, but the upper layer with high water resistance is maintained while being shielded from the atmosphere. By covering with the insulating film, there is no possibility that moisture in the atmosphere will be adsorbed or occluded on the surface of the lower insulating film. Further, as compared with the case of once being exposed to the atmosphere, maintaining the state of being shielded from the atmosphere also leads to suppressing a decrease in throughput.

When the lower layer insulating film and the upper layer insulating film are formed, if the plasma CVD method is applied, the film can be formed at a low temperature, so that the low melting point material layer such as the Al-based wiring already formed is damaged. Never give. Also, R
By optimizing the plasma discharge conditions such as F electric power, it becomes possible to generate desired chemical species from the source gas. By generating plasma intermittently, it is possible to prevent temperature rise due to radiant heat due to plasma, and it is also possible to prevent a large amount of chemical species other than the desired chemical species from being generated and accumulated.

[0036]

EXAMPLES The method for forming an insulating film according to the present invention will be described below with reference to specific examples. Here, as the passivation film on the Al-based wiring, a lower layer insulating film formed using an organic Si compound and an inorganic Si compound or an organic S compound.
An example of forming a laminated insulating film including an upper insulating film formed by using the i compound will be described.

In each of the following examples, a parallel plate type plasma CVD apparatus was used as the CVD apparatus. In this plasma CVD apparatus, a wafer is placed on the lower electrode and RF power is applied to the upper electrode. In addition, the temperature of the wafer can be adjusted by providing a heater on the lower electrode. On the other hand, the upper electrode is a shower electrode for uniformly supplying the source gas onto the substrate.

Example 1 In this example, tetradimethylaminosilane [(C
After forming the lower insulating film using H ₃ ) ₂ N] ₄ Si,
The upper insulating film was formed using a mixed gas of silane SiH ₄ , ammonia NH _3, and nitrogen N ₂ .

Specifically, as shown in FIG.
An SiO-based interlayer insulating film 2 is formed on a substrate 1, and an Al-based wiring 3 with a thickness of 0.8 μm and a wiring distance of 0.4 μm
Plasma CV under the following conditions for the wafer on which the
D was given.

Plasma CVD conditions Source gas: [(CH ₃ ) ₂ N] ₄ Si 100 sccm RF power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer temperature: 400 ° C. Electrode distance: 10 mm As shown in FIG. Thus, the lower insulating film 4 made of a SiN-based thin film was formed to a film thickness of 0.4 μm.
Then, after purging the plasma reaction chamber in which the above-described film formation is performed, the upper insulating film 5 made of a SiN-based thin film is continuously removed in the same plasma reaction chamber under the following conditions. The film was formed to a film thickness of 0.6 μm.

Plasma CVD conditions Source gas: SiH ₄ 250 sccm NH ₃ 100 sccm N ₂ 4000 sccm RF power: 350 W (13.56 MHz) Pressure: 1330 Pa Wafer temperature: 400 ° C. Electrode distance: 10 mm As a result, the lower insulating film 4 and the upper insulating layer are formed. A laminated insulating film 6 made of the film 5 was formed. The lower insulating film 4 does not have voids or cracks and has excellent step coverage, and its surface is relatively flat,
The upper insulating film 5 formed on this was also obtained with excellent coverage.

It should be noted that the lower insulating film 4 showed good step coverage because in the organic Si compound, the methyl group is easily liberated from the dimethylamino group, so that the Si-
The intermediate product, which retains the N bond, forms a high molecular weight polymer,
This is because it showed excellent fluidity.

Then, the above-mentioned wafer was subjected to a corrosion test. The conditions of this corrosion test are shown below.

Corrosion test conditions Hydrochloric acid concentration: 5% Test time: 5 minutes Solution temperature: 25 ° C. As a result of this corrosion test, no corrosion was observed on the Al-based wiring 3 and the laminated insulating film 6 formed was good. It was found that the product exhibits excellent water resistance and corrosion resistance. After the corrosion test, the Al-based wiring 3 was not corroded even if left in the atmosphere for a long time.

This is because the upper insulating film 5 was formed as a film having excellent water resistance and corrosion resistance without taking in hydrocarbon groups, so that the laminated insulating film 6 as a whole has sufficient water resistance and corrosion resistance. This is because the sex was secured.

Example 2 In this example, a lower insulating film is formed using a mixed gas of bisdimethylaminodiethoxysilane [(CH ₃ ) ₂ N] ₂ Si (OC ₂ H ₅ ) ₂ and NH _3. And then SiH ₄
An upper insulating film was formed using a mixed gas of N ₂ and N ₂ .

Specifically, as in Example 1, SiO
As shown in FIG. 2, a lower layer insulating film 4 made of a SiON-based thin film having a film thickness of 0.4 μm is formed on the wafer on which the system-based interlayer insulating film 2 and the Al-based wiring 3 are formed by plasma CVD under the following conditions. It was formed into a film.

Plasma CVD conditions Source gas: [(CH ₃ ) ₂ N] ₂ Si (OC ₂ H ₅ ) ₂ 100 sccm NH ₃ 50 sccm RF power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer temperature: 200 ° C. Distance between electrodes : 10 mm After purging the plasma reaction chamber in which the above-mentioned film formation is performed, subsequently, in the same plasma reaction chamber, under the following conditions, as shown in FIG. Was formed into a film having a thickness of 0.6 μm.

Plasma CVD conditions Raw material gas: SiH ₄ 250 sccm N ₂ 2000 sccm RF power: 350 W (13.56 MHz) Pressure: 1330 Pa Wafer temperature: 400 ° C. Electrode distance: 10 mm As a result, the lower insulating film 4 and the upper insulating film 5 The laminated insulating film 6 is formed. The lower insulating film 4 does not have voids or cracks and has excellent step coverage, and its surface is relatively flat,
The upper insulating film 5 formed on this was also obtained with excellent coverage.

The lower insulating film 4 showed good step coverage because in the organic Si compound, the ethoxy group is easily liberated from the Si atom and the methyl group is easily liberated from the dimethylamino group. -N
This is because the intermediate product, which retains the bond, forms a high-molecular polymer and exhibits excellent fluidity.

After that, when a corrosion test was conducted in the same manner as in Example 1, no corrosion occurred on the Al-based wiring 3. From this, it was found that the upper insulating film 4 had good water resistance and corrosion resistance, and thus the laminated insulating film 6 also had good film quality.

Example 3 In this example, hexadimethylaminodisilane [(CH
₃ ) A lower layer insulating film was formed using a mixed gas of ₂ N] ₆ Si ₂ and N _2, and then an upper layer insulating film was formed using a mixed gas of SiH ₄ and NH ₃ and N ₂ .

Specifically, as in Example 1, SiO
As shown in FIG. 2, a lower layer insulating film 4 made of a SiN-based thin film having a thickness of 0.4 μm is formed by plasma CVD under the following conditions on the wafer on which the system-based interlayer insulating film 2 and the Al-based wiring 3 are formed. It was formed into a film.

Plasma CVD conditions Raw material gas: [(CH ₃ ) ₂ N] ₆ Si ₂ 100 sccm N ₂ 500 sccm RF power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer temperature: 200 ° C. Electrode distance: 10 mm After purging the film-formed plasma reaction chamber, the upper insulating film 5 made of a SiN-based thin film as shown in FIG. A film having a thickness of 6 μm was formed.

As a result, the laminated insulating film 6 including the lower insulating film 4 and the upper insulating film 5 was formed. The lower insulating film 4 has no voids or cracks and is excellent in step coverage. Since the surface of the lower insulating film 4 is relatively flat, the upper insulating film 5 formed on the lower insulating film 4 also has excellent coverage. It was obtained at.

The lower insulating film 4 showed good step coverage because the methyl group was easily released from the dimethylamino group in the organic Si compound.
This is because the intermediate product that retains the i-N bond forms a high-molecular polymer and exhibits excellent fluidity.

The lower insulating film 4 in this embodiment is
An organic Si compound having a Si—Si bond is used as a raw material gas, and the Si—Si bond is easily broken. Therefore, the film formation is performed at a film formation speed about twice that of the first embodiment. It was

After that, when a corrosion test was conducted in the same manner as in Example 1, no corrosion was found on the Al-based wiring 3. From this, it was found that the upper insulating film 4 had good water resistance and corrosion resistance, and thus the laminated insulating film 6 also had good film quality.

Example 4 In this example, a lower insulating film was formed using biscyclopentadienylsilylazide Cp ₂ Si (N ₃ ) ₂ (where Cp represents a cyclopentadienyl group). After that, an upper insulating film was formed using a mixed gas of Cp ₂ Si (N ₃ ) ₂ and N ₂ .

Specifically, as in Example 1, SiO
As shown in FIG. 2, a lower layer insulating film 4 made of a SiN-based thin film having a thickness of 0.4 μm is formed by plasma CVD under the following conditions on the wafer on which the system-based interlayer insulating film 2 and the Al-based wiring 3 are formed. It was formed into a film.

Plasma CVD conditions Raw material gas: Cp ₂ Si (N ₃ ) ₂ 100 sccm RF power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer temperature: 200 ° C. Electrode distance: 10 mm Then, the above film formation was performed. In the same plasma reaction chamber as described above, plasma CVD under the following conditions is performed, and the upper insulating film 5 made of a SiN-based thin film as shown in FIG.
A film having a thickness of μm was formed.

Plasma CVD Conditions Source Gas: Cp ₂ Si (N ₃ ) ₂ 100 sccm N ₂ 2000 sccm RF Power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer Temperature: 200 ° C. Electrode Distance: 10 mm And the laminated insulating film 6 including the upper insulating film 5 was formed. The lower insulating film 4 has no voids or cracks and is excellent in step coverage, and the upper insulating film 5 formed thereon has excellent coverage.

The lower insulating film 4 showed good step coverage because the cyclopentadienyl group was easily liberated in the organic Si compound, and thus Si-N
This is because the intermediate product, which retains the bond, forms a high-molecular polymer and exhibits excellent fluidity. In addition, the upper insulating film 5
Is a film formed using an organic Si compound, and therefore, even if N ₂ withdraws a hydrocarbon group before the intermediate product forms a high molecular weight polymer, sufficient coverage was exhibited.

Then, an annealing treatment was performed under the following conditions.

Annealing conditions Introduced gas: The above raw material gas diluted with N ₂ gas containing 3% H ₂ 8000 sccm Annealing time: 60 minutes Pressure: Atmospheric pressure Annealing temperature: 400 ° C. Then, in the same manner as in Example 1, When a corrosion test was conducted, no corrosion was found on the Al-based wiring 3, and the laminated insulating film 6
Was found to exhibit good water resistance and corrosion resistance. This is because N ₂ acts as a reducing agent for the hydrocarbon group and the upper insulating film 5 having a low hydrocarbon group content is formed.

Example 5 In this example, bisdimethylaminosilyl azide [(C
H ₃ ) ₂ N] ₂ Si (N ₃ ) ₂ is used to form a lower insulating film, and then the [(CH ₃ ) ₂ N] ₂ Si (N ₃ ) ₂ and N
A film forming process using a mixed gas of H ₃ and hydrazine (N
_The post-treatment process using ₂ H ₄ ) was alternately repeated to form the upper insulating film.

Specifically, as in Example 1, SiO
As shown in FIG. 2, a lower layer insulating film 4 made of a SiN-based thin film having a thickness of 0.4 μm is formed by plasma CVD under the following conditions on the wafer on which the system-based interlayer insulating film 2 and the Al-based wiring 3 are formed. It was formed into a film.

Plasma CVD conditions Raw material gas: [(CH ₃ ) ₂ N] ₂ Si (N ₃ ) ₂ 100 sccm RF power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer temperature: 200 ° C. Electrode distance: 10 mm In the same plasma reaction chamber where the film formation was performed under the following conditions.
VD and plasma treatment for post-treatment were alternately repeated 6 times.

Plasma CVD Conditions Raw Material Gas: [(CH ₃ ) ₂ N] ₂ Si (N ₃ ) ₂ 100 sccm NH ₃ 50 sccm RF Power: 350 W (13.56 MHz) Pressure: 1200 Pa Wafer Temperature: 200 ° C. Electrode Distance: 10 mm Film formation time: 6 seconds Plasma processing conditions Post-treatment gas: N ₂ H ₄ 100 sccm RF power: 350 W (13.56 MHz) Pressure: 1330 Pa Wafer temperature: 150 ° C. Electrode distance: 10 mm Processing time: 60 seconds Post-treatment is performed each time a film is formed by 1 μm, and a SiN-based upper layer insulating film 5 having a total thickness of 0.6 μm is formed as shown in FIG. 3, and as a result, the lower layer insulating film 4 and the upper layer insulating film 4 are formed. A laminated insulating film 6 made of the film 5 was formed. The lower insulating film 4 has no voids or cracks and is excellent in step coverage, and the upper insulating film 5 formed thereon has excellent coverage.

The lower insulating film 4 showed good step coverage because the methyl group was easily liberated from the dimethylamino group in the organic Si compound.
This is because the intermediate product that retains the i-N bond forms a high-molecular polymer and exhibits excellent fluidity. Further, the reason why the upper insulating film 5 showed good coverage is that N ₂ H ₄ was not mixed with the organic Si compound and was not used, so that polymerization of the intermediate product was not hindered.

Subsequently, as in the case of Example 4, an annealing treatment was performed using an introduction gas diluted with the source gas, and a corrosion test was conducted. As a result, no corrosion was observed on the Al-based wiring 3 and the laminated insulating film 6 It was found that, as with the film formed in Example 1, shows good water resistance and corrosion resistance. In this case, the SiN-based upper insulating film 5 is formed by repeating reduction of hydrocarbon groups with N ₂ H ₄ , and the content of hydrocarbon groups is low from the surface layer portion to the deep layer portion. It is due to the fact.

As described above, the laminated insulating film 6 formed according to Examples 1 to 5 exhibits good coverage and is excellent in water resistance and corrosion resistance, and therefore, is used as a passivation film. It was suitable to be used.

Although the example in which the method for forming an insulating film according to the present invention is applied has been described above, the present invention is not limited to the above-mentioned embodiments. For example, the insulating film formed by applying the present invention can be applied as an interlayer insulating film other than the passivation film. Further, the structure of the CVD apparatus for forming the insulating film is not limited to the parallel plate type plasma CVD apparatus shown in the embodiment, and may be, for example, ECR-CV.
It may be a D device. Furthermore, the CVD conditions, the annealing conditions, and the configuration of the wafer on which the insulating film is formed are not particularly limited, and for example, after forming the lower insulating film using an organic Si compound and before forming the upper insulating film. May be annealed.

[0074]

As is apparent from the above description, application of the present invention makes it possible to achieve both step coverage, which has been difficult in the past, and film quality such as insulation resistance and water resistance. Therefore, it is possible to improve the performance and yield of semiconductor devices based on fine design rules.

Further, by continuously forming the lower insulating film and the upper insulating film, it is possible to suppress a decrease in throughput.

Therefore, a highly reliable semiconductor device can be provided without increasing the cost, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic view of a Si substrate according to an embodiment of the present invention.
It is a schematic diagram which shows the cross section of the wafer in which the O type interlayer insulation film and the Al type wiring were formed.

FIG. 2 is a schematic view showing a state in which a lower insulating film is formed on the wafer of FIG.

FIG. 2 is a schematic view showing a state in which an upper insulating film is further formed on the wafer of FIG.

FIG. 4 is a schematic view showing a cross section of a wafer on which a SiN-based insulating film is formed by a conventional method.

[Explanation of symbols]

 1 Si substrate 2 SiO-based interlayer insulating film 3 Al-based wiring 4 Lower layer insulating film 5 Upper layer insulating film 6 Laminated insulating film

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[Procedure amendment]

[Submission date] November 18, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic view of a Si substrate according to an embodiment of the present invention.
It is a stylistic view showing a cross section of a wafer on which an O-based interlayer insulating film and an Al-based wiring are formed.

2 is a stylistic diagram showing a state in which a lower insulating film is formed on the wafer of FIG.

FIG. 3 is a pattern diagram showing a state in which an upper insulating film is further formed on the wafer of FIG.

FIG. 4 is a stylistic view showing a cross section of a wafer on which a SiN-based insulating film is formed by a conventional method.

[Explanation of reference numerals] 1 Si substrate 2 SiO-based interlayer insulating film 3 Al-based wiring 4 Lower layer insulating film 5 Upper layer insulating film 6 Laminated insulating film

Claims (8)

[Claims] 1. A SiN-based thin film or S is formed on a substrate by using a source gas containing an organic Si compound having a Si—N bond.
a step of depositing a lower insulating film made of an iON-based thin film having a relatively high hydrocarbon group content by CVD; and a relatively low hydrocarbon group content made of a SiN-based thin film on the lower insulating film. And a step of forming an upper insulating film by CVD. 2. The upper insulating film is formed of an inorganic Si compound and N.
_The method for forming an insulating film according to claim 1, wherein the film formation is performed using a mixed gas containing ₂ and / or a compound containing an N atom. 3. The method for forming an insulating film according to claim 2, wherein the inorganic Si compound is SiH ₄ . 4. The upper insulating film is formed of an organic Si compound and N 2.
_The method for forming an insulating film according to claim 1, wherein the film is formed using a compound containing ₂ and / or N atoms. 5. The method for forming an insulating film according to claim 4, wherein the organic Si compound has a Si—N bond. 6. The compound according to claim 2, wherein the compound containing N atom is NH _3.
The method for forming an insulating film according to item. 7. The upper layer insulating film is formed after the lower layer insulating film is formed, while the substrate is kept in a state of being shielded from the atmosphere.
The method for forming an insulating film according to any one of 1. 8. The method of forming an insulating film according to claim 1, wherein the film formation is performed while generating plasma.