JP3336770B2 - Method of forming insulating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a silicon nitride (SiN) -based insulating film or a silicon oxynitride (SiON) -based insulating film used as a final protective film or an interlayer insulating film of a wafer in a semiconductor device, for example. The present invention relates to a method for forming an insulating film formed by a chemical vapor deposition (hereinafter, referred to as CVD) method using an organic Si compound as a source gas.

[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, a so-called passivation film. When forming the SiN-based insulating film, the plasma CV is used so as not to damage the low-melting-point material layer such as the aluminum (Al) -based wiring that has already been formed.
Film formation is performed at a low temperature by Method D. Conventionally, silane (SiH ₄ ) / ammonia (NH)
₃ ) A mixed gas, a mixed gas of SiH ₄ / nitrogen (N ₂ ) and the like have been used.

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

As a method for improving the step coverage, it has been proposed to control the plasma state by a two-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 an electrode on a side on which a wafer is mounted, and MHz is applied to other electrodes.
A high-frequency RF voltage of the order is applied to increase the low-energy ion bombardment to improve the 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 step, and the conformal film formation has not yet been achieved.

[0005] Therefore, SiN having even better coverage is provided.
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 is [(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 having} Si, N, C, and H atoms as main constituent elements and having a bond (Si—N bond) between a silicon atom and a nitrogen atom. When this is used as a source gas to form a film, the presence of the Si—N bond enables efficient formation of a SiN-based insulating film. In addition, when a hydrocarbon group is cleaved from the organic Si compound at the time of film formation, an intermediate product having a Si—N bond is easily polymerized, and the fluidity is increased. It is believed that a system insulating film can be formed.

[0006]

However, in the SiN-based insulating film formed using an organic Si compound as described above, the insulation resistance is deteriorated due to the remaining hydrocarbon groups, and the water resistance and corrosion resistance are reduced. It is feared that the properties are deteriorated.
If such a SiN-based insulating film is applied as a passivation film and an interlayer insulating film, the reliability of the semiconductor device may be reduced.

Accordingly, the present invention has been proposed in view of such conventional circumstances, and provides a method of forming an insulating film capable of suppressing incorporation of a hydrocarbon group while ensuring excellent coverage. With the goal.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies on achieving the above object and as a result, have come to propose the following two methods.

According to a first aspect of the invention, there is provided a film forming step of forming an insulating film on a substrate by a CVD method using an organic Si compound having a Si—N bond, And a post-processing step of performing a plasma process on the insulating film in an atmosphere.

[0010] The post-treatment gas containing at least N atoms in the molecule functions to extract the hydrocarbon group component taken in the insulating film. As the post-treatment gas, in addition to the _{N 2,} hydrogen azide _{(N 3 H), NH 3} , ammonia derivatives, hydrazine _{(N 2 H} 4), such as hydrazine derivatives such as methylhydrazine, the H atoms in the molecule Can also be used. Since the latter compound gas is more easily decomposed in plasma than N ₂ gas, it is considered that the function of extracting the hydrocarbon group component from the insulating film is even stronger.

In order to further reduce the amount of the hydrocarbon group component, it is preferable to form the insulating film to a desired film thickness by alternately repeating the film forming step and the post-processing step a plurality of times. Thus, the hydrocarbon-based component can be sufficiently removed not only in the surface layer portion of the insulating film but also in the deep layer portion.

On the other hand, a second invention is to form an insulating film on a substrate by a CVD method using a mixed gas containing an organic Si compound having an Si—N bond and an organic nitrogen compound.

Of course, in combination with the above-described first aspect of the present invention, after forming an insulating film having a small amount of a hydrocarbon group component with good coverage by forming a film using an organic nitrogen compound as described above, at least Plasma treatment in an atmosphere of a post-treatment gas containing N atoms may further reduce the hydrocarbon group component in the surface layer of the insulating film. Further, the insulating film may be formed by repeating the film formation using the organic nitrogen compound as described above and the plasma treatment in an atmosphere of a post-processing gas containing at least N atoms in the molecule.

Here, as the organic nitrogen compound, a hydrazine derivative having at least one alkyl group or phenyl group is preferably used.

In any of the above-described methods for forming an insulating film, an organic Si compound having a Si—N bond is used as a source gas at the time of film formation. As the organic Si compound, an azide group (hereinafter referred to as —N ₃ )), -N
A structure in which an R ₂ group (where R is a hydrocarbon group having 1 or more carbon atoms) is bonded to a Si atom is preferable. In particular, in the case where —NR ₂ is bonded to a Si atom, an intermediate product formed by cutting a hydrocarbon group during film formation is easily polymerized and the fluidity is increased, so that the effect of improving coverage is improved. Excellent.

Further, when an alkyl group (hereinafter, referred to as —R ′ group) and / or an alkoxyl group (hereinafter, referred to as —OR ″ group) are bonded to the Si atom, these are formed during film formation. The cleavage of the —R ′ group or the —OR ″ group increases the fluidity of the generated intermediate product and improves the coverage.

Further, the organic Si having the Si—N bond
The compound may have a structure in which a fluorine (F) atom is bonded to a Si atom. When the F atoms are bonded, the polymerization reaction at the time of film formation is promoted, coverage can be improved, and the dielectric constant of the formed insulating film can be reduced.

The H atom directly bonded to the Si atom is
Unlike the above-described —NR ₂ group, —N ₃ group, —R ′ group, and —OR ″ group, they do not exhibit the effect of improving the film formation efficiency or the coverage by maintaining the Si—N bond. So
It is better not to bond any single atom to the Si atom, or it is better to have a small number of bonded atoms.

Further, an organic Si compound having a Si--Si bond may be used to improve the film forming speed. Thus, the film formation rate can be improved without increasing the flow rate of the source gas supplied at the time of film formation or increasing the power applied to the electrodes of the plasma CVD apparatus. Throughput can be improved without causing a problem such as deterioration of coverage.

Therefore, among the organic Si compounds that can be used as a source gas, those having the most desirable structure can be represented by the following general formula (1).

Sin (NR ₂ ) w (N ₃ ) x (R ′) y (OR ″) z Fv (1) (where v, w, x, y, and z are v + w + x + y + z =
2n + 2, 0 ≦ w ≦ 2n + 2, 0 ≦ x ≦ 2n + 2, 1 ≦
w + x ≦ 2n + 2, 0 ≦ y ≦ 2n + 1, 0 ≦ z ≦ 2n +
1, 0 ≦ v ≦ 2n + 1, where n is an integer of 1 or more. R, R 'and R''each represent 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 a saturated hydrocarbon or an 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 has no —OR ″ group bonded thereto, this is used as a source gas, and an oxygen-based gas is added thereto. If they are not mixed, a SiN-based thin film will be formed. On the other hand, when x ≧ 1, that is, when an organic Si compound to which an —OR ″ group is bonded, when this is used as a source gas, a small amount of O atoms are taken in during film formation, so that an oxygen-based gas The SiON-based thin film can be formed without using both.

Further, when forming a film, it is possible to perform a treatment at a low temperature without damaging a low melting point material layer such as an Al-based wiring already formed. It is preferable to perform CVD. The plasma CVD apparatus to be used may be a parallel plate type plasma CVD apparatus, or a magnetic field microwave plasma CVD (E) capable of generating high-density plasma under low pressure.
CR-CVD) equipment and inductively coupled plasma CVD (IC)
P-CVD) equipment, helicon wave plasma CVD equipment, T
It may be a CP-CVD device.

When forming a film by plasma CVD,
In addition to the desired insulating film components, intermediate products, by-products, undissociated components of the raw material gas, and the like also exist near the substrate surface, so that these impurity components and particles are prevented from being taken into the film. The plasma may be generated intermittently.

[0025]

According to the present invention, when an organic Si compound having a Si—N bond is used as a source gas, a hydrocarbon group component is preferentially cut from the organic Si compound during film formation,
Since the chemical species in which the Si-N bond persisted are bonded to each other,
The intermediate product is polymerized and exhibits fluidity. And
Thereby, the step coverage of the insulating film is improved.

Further, when plasma treatment is performed in an atmosphere of a post-processing gas containing N atoms in the molecule after the film formation, the hydrocarbon group components taken in the insulating film are extracted by the N atoms. If a gas further containing H atoms is used as the post-treatment gas, the H atoms also play a role in extracting the hydrocarbon group components in the insulating film. It is possible to further reduce.

When the insulating film is formed by alternately repeating the film forming step and the post-processing step a plurality of times, the hydrocarbon-based component is sufficiently removed not only in the surface layer of the insulating film but also in the deep layer. Becomes an insulating film.

The gas containing at least N atoms in the molecule functions to extract a hydrocarbon group component even when supplied at the time of forming the insulating film. However, a large amount of an inorganic gas such as N ₂ gas or NH ₃ gas is used. If supplied, the hydrocarbon group component may be extracted before the intermediate product generated from the organic Si compound is polymerized, thereby reducing the fluidity. On the other hand, when the organic nitrogen compound gas is used, the hydrocarbon group component can be extracted while maintaining good fluidity.

In particular, hydrazine derivatives having an alkyl group or a phenyl group are excellent in catalysis for accelerating the polymerization reaction of an intermediate product, for introducing an N atom into this product, and for extracting hydrocarbon group components. Not only
The presence of the alkyl group or the phenyl group also has the effect of reducing the probability of the intermediate product adhering to the substrate, so that good step coverage can be maintained.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for forming an insulating film according to the present invention will be described with reference to specific embodiments and a preceding example. Here, Al
An example in which a SiN-based insulating film or a SiON-based insulating film is formed as a passivation film on a system wiring will be described.

In each of the following examples and embodiments, C
As the VD apparatus, a parallel plate type plasma CVD apparatus was used. In this plasma CVD apparatus, a wafer is placed on a lower electrode, and RF power is applied to an upper electrode. The lower electrode is provided with a heater so that the wafer temperature can be adjusted. on the other hand,
The upper electrode serves as a shower electrode for uniformly supplying the source gas onto the substrate.

First, some preceding examples of the present invention will be described.

Prior Example 1 In this example, trisdimethylaminosilyl azide [(CH ₃ ) ₂ N] ₃ SiN ₃ was used as the organic Si compound.
And then post-processed with N ₂ to form Si
An N-based insulating film was formed.

More specifically, first, a plasma CV under the following conditions is placed on a wafer having an SiO-based interlayer insulating film 2 and an Al-based wiring 3 formed on a Si substrate 1 as shown in FIG.
By D, the SiN-based insulating film 4 was formed to a thickness of 1 μm.

Plasma CVD conditions Source gas: [(CH ₃ ) ₂ N] ₃ SiN ₃ Flow rate 100
sccm RF power: 350 W (13.56 MHz) (applied to upper electrode) Pressure: 1200 Pa Wafer temperature: 200 ° C. Distance between electrodes: 10 mm Film formation time: 60 seconds The obtained SiN-based insulating film 4 is shown in FIG. like,
It was excellent in step coverage without voids and cracks.

Subsequently, a plasma treatment under the following conditions was performed as a post-treatment.

Plasma processing conditions Post-processing gas: N ₂ flow rate 100 sccm RF power: 350 W (13.56 MHz) Pressure: 1330 Pa Wafer temperature: 400 ° C. Inter-electrode distance: 10 mm By this processing, SiN-based insulating film 4 is contained. Hydrocarbon-based components have been reduced.

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

Annealing conditions Introduced gas: Diluted above raw material gas with 3% H ₂ containing N ₂ gas Flow rate 8000 sccm Annealing time: 60 minutes Pressure: Atmospheric pressure Annealing temperature: 400 ° C. The passivation film composed of the film 4 was completed.

Here, a corrosion test was performed on the wafer on which the passivation film made of the SiN-based insulating film 4 was formed. 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. Thus, the SiN formed as described above
It was found that the system insulating film 4 exhibited good water resistance and corrosion resistance.

Preceding Example 2 In this example, bisdimethylaminosilyldiazide [(CH ₃ ) ₂ N] ₂ Si (N ₃ ) ₂ was used as the organic Si compound.
After forming a film using a mixed gas of NH ₃ and NH ₃ , post-treatment was performed using NH ₃ to form a SiN-based insulating film.

More specifically, on the same wafer as in the first embodiment, the raw material gas was changed to [(CH ₃ ) ₂ N] ₂ Si (N ₃ ) ₂ :
Plasma CV under the same conditions as in the preceding example 1 except that the flow rate was changed to 100 sccm and NH ₃ : the flow rate was changed to 50 sccm.
D was used to form a SiN-based insulating film 4 having a thickness of 1 μm. The SiN-based insulating film 4 thus formed is
It was excellent in step coverage without voids and cracks.

Subsequently, the post-treatment gas is NH ₃ : flow rate 100
The plasma processing was performed in the same manner as in the previous example 1 except that the temperature was changed to sccm and the wafer temperature was changed to 150 ° C. By this treatment, the hydrocarbon group component contained in the SiN-based insulating film 4 could be reduced.

[0045] Further, the raw material gas 3% _{H 2} containing _{N 2}
Annealing treatment was performed in the same manner as in Example 1 except that a gas diluted with a gas was used, and a passivation film made of the SiN-based insulating film 4 was completed.

Here, a corrosion test was performed on the wafer on which the passivation film made of the SiN-based insulating film 4 was formed in the same manner as in the first example.
Did not show any corrosion. From this, it was found that the SiN-based insulating film 4 exhibited good water resistance and corrosion resistance.

Next, an embodiment of the present invention will be described.

Example 1 In this example, a SiN-based insulating film was formed by alternately repeating a film forming step and a post-processing step using N ₂ H ₄ .

More specifically, the SiN-based insulating film 4 was formed on the same wafer as in the first example by plasma CVD under the same conditions as in the second example except that the film formation time was changed to 6 seconds.
The film was formed to a thickness of 00 nm. The SiN-based insulating film 4 formed as described above had no voids or cracks and was excellent in step coverage.

Subsequently, the post-processing gas was N ₂ H ₄ : flow rate 10
The plasma processing was performed in the same manner as in the previous example 2 except that the processing time was changed to 0 sccm and the processing time was set to 60 seconds. By this treatment, the hydrocarbon group component contained in the SiN-based insulating film 4 could be reduced.

Thereafter, the above-mentioned film forming step and post-processing step are alternately repeated nine times, and finally a 1 μm thick SiN film is formed.
A system insulating film 4 was formed. As a result, the SiN-based insulating film 4 in which the hydrocarbon group component was reduced from the surface portion to the deep portion was formed.

[0052] Further, the raw material gas 3% _{H 2} containing _{N 2}
Annealing treatment was performed in the same manner as in Example 1 except that a gas diluted with a gas was used, and a passivation film made of the SiN-based insulating film 4 was completed.

Here, a corrosion test was performed on the wafer on which the passivation film made of the SiN-based insulating film 4 was formed in the same manner as in the first example.
Did not show any corrosion. From this, it was found that the SiN-based insulating film 4 exhibited good water resistance and corrosion resistance.

Example 2 In this example, tetradimethylaminodifluorodisilane [(CH ₃ ) ₂ N] ₄ Si ₂ F ₂ was used as the organic Si compound.
And a dimethylhydrazine (CH ₃ ) ₂ N ₂ H ₂ mixed gas to form a SiN-based insulating film.

More specifically, on the same wafer as in the first embodiment, the raw material gas was [(CH ₃ ) ₂ N] ₄ Si ₂ F ₂ : flow rate 100 sccm, (CH ₃ ) ₂ N ₂ H ₂ : flow rate 50 sc
The SiN-based insulating film 4 was formed to a thickness of 1 μm by plasma CVD under the same conditions as in the previous example 2 except that the thickness was changed to cm.

The SiN-based insulating film 4 thus formed had no voids or cracks, was excellent in step coverage, and had a reduced hydrocarbon group component.

[0057] Further, the raw material gas 3% _{H 2} containing _{N 2}
Annealing treatment was performed in the same manner as in Example 1 except that a gas diluted with a gas was used, and a passivation film made of the SiN-based insulating film 4 was completed.

Here, a corrosion test was performed on the wafer on which the passivation film made of the SiN-based insulating film 4 was formed in the same manner as in the first example.
Did not show any corrosion. From this, it was found that the SiN-based insulating film 4 exhibited good water resistance and corrosion resistance.

Example 3 In this example, bisdimethylaminobisethoxydifluorodisilane [(CH ₃ ) ₂ N] ₂ was used as an organic Si compound.
Si ₂ (OC ₂ H ₅ ) F ₂ and diethyl hydrazine (C ₂
An SiON-based insulating film was formed using a mixed gas with H ₅ ) ₂ N ₂ H ₂ .

More specifically, on the same wafer as in the first embodiment, the raw material gas was supplied as [(CH ₃ ) ₂ N] ₂ Si ₂ (OC ₂ H).
₅ ) F ₂ : flow rate 100 sccm, (C ₂ H ₅ ) ₂ N ₂ H
₂ : Preceding example 1 except that the flow rate was changed to 50 sccm
The SiON-based insulating film 5 was formed to a thickness of 1 μm by plasma CVD under the same conditions as in the above.

The SiON-based insulating film 5 thus formed had no voids or cracks, was excellent in step coverage, and had a reduced hydrocarbon group component.

[0062] Further, the raw material gas 3% _{H 2} containing _{N 2}
Annealing was performed in the same manner as in the first example except that a gas diluted with a gas was used, thereby completing a passivation film made of the SiON-based insulating film 5.

Here, when a corrosion test was performed on the wafer on which the passivation film made of the above-mentioned SiON-based insulating film 5 was formed in the same manner as in the first example, no corrosion was observed on the Al-based wiring 3. Was. From this, it was found that the SiON-based insulating film 5 exhibited good water resistance and corrosion resistance.

Example 4 In this example, a SiN-based insulating film was formed using a mixed gas of tetradimethylaminosilane [(CH ₃ ) ₂ N] ₄ Si and phenylhydrazine C ₆ H ₅ NHNH ₂ as an organic Si compound. Filmed.

Specifically, on the same wafer as in the first embodiment, the raw material gas was supplied with [(CH ₃ ) ₂ N] ₄ Si at a flow rate of 100
sccm, C ₆ H ₅ NHNH ₂ : Plasma C under the same conditions as in the preceding example 1 except that the flow rate was changed to 50 sccm.
The SiN-based insulating film 4 was formed to a thickness of 1 μm by VD.

The SiN-based insulating film 4 thus formed was free of voids and cracks, had excellent step coverage, and had a reduced hydrocarbon group component.

[0067] Further, the raw material gas 3% _{H 2} containing _{N 2}
Annealing treatment was performed in the same manner as in Example 1 except that a gas diluted with a gas was used, and a passivation film made of the SiN-based insulating film 4 was completed.

Here, a corrosion test was performed on the wafer on which the passivation film made of the above-described SiN-based insulating film 4 was formed in the same manner as in the first example.
Did not show any corrosion. From this, it was found that the SiN-based insulating film 4 exhibited good water resistance and corrosion resistance.

As described above, the method of forming the insulating film shown in Examples 1 to 4 has a difference between removing the hydrocarbon component during the post-processing and removing the hydrocarbon component during the film formation. However, in each case, it was possible to provide the SiN-based insulating film 4 or the SiON-based insulating film 5 in which the content of the hydrocarbon group component was suppressed. Further, these insulating films also show good coverage, and thus were suitable as passivation films.

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-described embodiment. For example, an interlayer insulating film other than a passivation film can be formed by applying the present invention. Further, the formation of the SiN-based insulating film 4 or the SiON-based insulating film 5 according to the second to fourth embodiments may be combined with the post-processing in the first embodiment. Further, the type of the source gas for forming the SiN-based insulating film 4 or the SiON-based insulating film 5, the film forming conditions, and the configuration of the wafer can be appropriately changed.

[0071]

As is apparent from the above description, when the present invention is applied, an insulating film having excellent step coverage and a reduced content of the hydrocarbon group component can be formed.

Therefore, the insulating film formed by applying the present invention has good insulating properties and excellent water resistance and corrosion resistance. Therefore, when this is used as a passivation film or an interlayer insulating film, a highly reliable semiconductor device in which deterioration of device characteristics is prevented can be formed.

[Brief description of the drawings]

FIG. 1 shows a process of manufacturing a semiconductor device by applying the present invention, in which a SiO-based interlayer insulating film and an A
FIG. 3 is a schematic diagram showing a cross section of a wafer on which l-system wiring is formed.

FIG. 2 is a schematic diagram showing a state where an insulating film is formed on the wafer of FIG. 1;

FIG. 3 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 A
1-system wiring, 4 SiN-based insulating film, 5 SiON-based insulating film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/318 H01L 21/768

Claims (3)

(57) [Claims] 1. A method for forming a SiN-based insulating film or a SiON-based insulating film, comprising forming an insulating film on a substrate by a chemical vapor deposition method using an organic silicon compound having a bond between silicon atoms and nitrogen atoms. A film forming step of forming a film, and a post-treatment gas or nitrogen containing at least a nitrogen atom in a molecule.
A post-processing step of performing plasma processing on the insulating film under an atmosphere of a post-processing gas containing atoms and hydrogen atoms, wherein the film forming step and the post-processing step are alternately repeated a plurality of times. Method for forming an insulating film. 2. A method for forming an SiN-based insulating film or a SiON-based insulating film, comprising: a step of forming an organic silicon compound having a bond between a silicon atom and a nitrogen atom and a hydrazine derivative having at least one or more alkyl groups or phenyl groups. A method for forming an insulating film, comprising forming an insulating film on a substrate by a chemical vapor deposition method using a mixed gas containing an organic nitrogen compound. 3. The method according to claim 1, wherein the film is formed while generating plasma.