JP3204041B2 - Method of forming insulating film - Google Patents

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, and is suitably applied to, for example, forming an interlayer insulating film in a semiconductor device having a multilayer wiring structure.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become more highly integrated, the minimum width of wiring has reached submicron, and the number of wiring layers has been increased.

Conventionally, a wiring pattern in a semiconductor device has been formed by using a thin film forming technique, a lithography technique, and an etching technique. However, in order to form a fine wiring pattern with high accuracy in a multilayer wiring structure,
It is indispensable to flatten the underlying surface of the wiring.

That is, in the manufacture of a semiconductor device,
After an element such as a transistor is formed on a semiconductor substrate such as a silicon (Si) substrate, an interlayer insulating film such as a silicon dioxide (SiO ₂ ) film or a silicon nitride (SiN) film is formed thereon by a CVD method. A wiring pattern is formed on the insulating film. Although the interlayer insulating film formed by this CVD method has high density and excellent insulating performance, it is formed in a similar shape to the underlying semiconductor substrate.
Irregularities corresponding to the irregularities on the surface of the semiconductor substrate appear on the surface. Therefore, it is necessary to flatten the surface of the interlayer insulating film before forming the wiring pattern.

As one of the methods for flattening the surface, there is a method in which a coating type insulating film is used as an interlayer insulating film, and the coating type insulating film is coated on an uneven semiconductor substrate. This coating type insulating film is roughly classified into an inorganic type and an organic type. Among them, as an inorganic coating type insulating film, a spin-on-glass (Spin-on-glass) which can be easily vitrified by spin-coating a raw material solution obtained by dissolving silanol in water or alcohol on a semiconductor substrate and then performing a heat treatment is used. on Glass, SOG) film (hereinafter “inorganic SOG film”)
That. ) Are well known.

The inorganic SOG film is an interlayer insulating film that can easily make the surface flat, and thus has been widely used. However, this inorganic SOG film is
Because it is highly hygroscopic and contains a lot of moisture in the film,
When used as an interlayer insulating film, the following problems occur.

That is, in the manufacture of a semiconductor device,
For example, as shown in FIG. 19, an inorganic SOG film 104 is spin-coated as an interlayer insulating film on the entire surface so as to cover a first wiring 103 formed on a semiconductor substrate 101 via an interlayer insulating film 102, and heat treatment is performed. By doing this inorganic SO
After vitrifying the G film 104, the inorganic SOG film 10
4, a contact hole 105 is formed by etching. Next, a second wiring 106 contacting the first wiring 103 through the contact hole 105 is formed by CVD.
At this time, heat is applied to release water from the inorganic SOG film 104, thereby causing poor filling of the contact hole 105 (for example, generation of voids) and adhesion to the inorganic SOG film 104. Peeling of the second wiring 106 due to the deterioration of the property occurs.

In order to solve these problems, in recent years,
An inorganic SOG film having improved moisture absorption resistance by including a silicon (Si) -hydrogen (H) bond has been developed. In such an inorganic SOG film containing a Si—H bond,
It is important how the Si-H bond remains even after going through various processes.

[0009]

However, according to the knowledge of the present inventors, it has been found that the inorganic SOG film 1 containing Si—H bonds
For example, when the heat treatment is performed at a temperature of 500 ° C. or more, or the chemical S04 is treated with a chemical such as a cleaning solution or a developer represented by an amine-based organic solvent, the inorganic SOG film 104 is heated or catalyzed by the chemical. The reaction in which the Si—H bond in the inside is broken is promoted. For this reason, the inorganic SOG film 104
Si-H bonds contained therein decrease, and as a result, moisture absorption resistance deteriorates.

That is, as shown in FIG. 19, when a resist, a developing solution, a cleaning solution, and the like used when forming the contact hole 105 come into contact with the inorganic SOG film 104, the Si—H bond is formed in the inorganic SOG film 104. Is generated, and its moisture absorption resistance is deteriorated. For this reason, voids are generated inside the contact hole 105 and the second wiring 106 is peeled off.
This reduces the reliability of the multilayer wiring structure.

FIGS. 20 and 21 show examples of the measurement results of the infrared absorption spectrum of the SOG film 104. FIG. 20 shows the measurement results after coating and heat treatment, and FIG. 21 shows the measurement results after cleaning with an amine-based organic cleaning liquid. Show. FIG. 20 and FIG.
As can be seen from FIG. 1, the SOG film 1 after application and heat treatment
In the infrared absorption spectrum of No. 04, an absorption peak due to a Si—H bond is observed around a wave number of 2300 cm ⁻¹ (FIG. 20), but SOG after washing with an amine-based organic washing solution.
No absorption peak due to this Si—H bond is observed in the infrared absorption spectrum of the film 104 (FIG. 21). This is because the SOG film 1 is cleaned by the amine-based organic cleaning solution.
This indicates that the Si-H bond in No. 04 was almost broken.

Accordingly, an object of the present invention is to provide a method of forming an insulating film capable of forming an insulating film having high moisture absorption resistance even after heat treatment or treatment with a chemical such as an amine-based organic solvent. To provide.

[0013]

In order to achieve the above object, a method for forming an insulating film according to the present invention comprises forming an inorganic coating type insulating film containing Si--H bonds on a substrate, and then forming the coating type insulating film on a substrate. The surface of the insulating film is subjected to a treatment using O ₂ ions as a main reactive species in an atmosphere at a pressure of 40 Pa or less.

In one embodiment of the present invention, after forming a contact hole in the coating type insulating film, the inner wall of the contact hole is subjected to a treatment using O ₂ ions as a main reactive species in an atmosphere at a pressure of 40 Pa or less. .

In the present invention, the upper limit of the pressure of the atmosphere of the treatment using O ₂ ions as the main reactive species is 40 Pa (≒ 0.3
At a pressure exceeding 40 Pa, O ₂ radicals become the main reactive species, making it difficult to obtain the effect of densification of the surface layer of the coating type insulating film. This is because cracks are easily formed.

In the present invention, in order to maintain the moisture absorption resistance of the coating type insulating film sufficiently high by densifying the surface layer, and to almost completely prevent cracks and the like from occurring, it is necessary to use O
The pressure of the atmosphere of the treatment in which _two ions are the main reactive species is preferably 6.6 to 13.3 Pa (≒ 0.05 to 0.1 To
rr).

In the present invention, a so-called hollow cathode type ashing apparatus is preferably used for the treatment using O ₂ ions as the main reactive species.
In this hollow cathode type ashing device, a large discharge current flows because the discharge impedance is small. That is, the density of the plasma is very high, and a large amount of O ₂ ions enter the surface of the substrate to be processed. In this case, this O ₂
Since the energy of ions is low, only the surface layer of the coating type insulating film is densified.

In the present invention, in the treatment using O ₂ ions as the main reactive species, the O ₂ ion density is generally lower than that of a hollow cathode type ashing device, but the parallel plate type reactive ion etching (RIE) device is used. May be used.

[0019]

According to the method of forming an insulating film according to the present invention having the above-described structure, after a coating type insulating film including a Si-H bond is formed on a substrate, a pressure is applied to the surface of the coating type insulating film. Is performed in an atmosphere of 40 Pa or less, using O ₂ ions as the main reactive species, whereby the surface layer of the coating type insulating film can be densified. For this reason,
Even if heat treatment or treatment with a chemical such as an amine-based organic solvent is performed thereafter, the reaction of breaking the Si—H bond in the coating type insulating film can be suppressed, and the reduction of the Si—H bond can be prevented. Can be. Thereby, the moisture absorption resistance of the coating type insulating film can be kept high.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIGS. 1 to 8 are sectional views showing a method of manufacturing a semiconductor device according to a first embodiment of the present invention in the order of steps.

In the method of manufacturing a semiconductor device according to the first embodiment, first, as shown in FIG. 1, a semiconductor substrate 1 such as a Si substrate on which elements such as transistors (not shown) are formed in advance. The first through the interlayer insulating film 2
Is formed.

Next, as shown in FIG. 2, an inorganic SOG film 4 containing a Si—H bond is spin-coated as an interlayer insulating film on the entire surface so as to cover the first wiring 3 and then heat-treated. This inorganic SOG film 4 is vitrified. The temperature of this heat treatment is a temperature at which the Si—H bond in the inorganic SOG film 4 is not broken, for example, about 400 ° C.

Next, as shown in FIG. 3, by performing an ashing process using O ₂ ions as main reactive species, inorganic S
The surface layer of the OG film 4 is densified (the portion densified by this ashing process is marked with “x”). This ashing process is performed by a hollow cathode type ashing device.
O ₂ flow rate 100 SCCM, RF power 200 W, pressure 1
This was performed for 1 minute under the condition of 3.3 Pa (≒ 0.1 Torr).

FIG. 9 shows an example of a hollow cathode type ashing apparatus used in the first embodiment. In FIG. 9, reference numeral 21 denotes a vacuum vessel. This vacuum vessel 21
Is evacuated by an evacuation system (not shown) connected to the evacuation port 21a, and O ₂ gas is introduced into the inside from the gas introduction port 21b. I have. In the vacuum vessel 21, a hollow cathode 22 including a lower electrode 22a and a mesh-shaped upper electrode 22b provided opposite to each other is provided. RF power is applied to the hollow cathode 22.
The substrate 23 to be processed is placed on the lower electrode 22a.

Next, as shown in FIG. 4, a resist pattern 5 having a predetermined shape is formed on the inorganic SOG film 4 by lithography. When the resist pattern 5 is formed, the surface of the inorganic SOG film 4 is brought into contact with a resist, a developing solution, water, or the like, and a reaction occurs in which Si—H bonds are cut.
As described above, since the surface layer of the inorganic SOG film 4 has been densified in advance by the ashing process, this reaction is suppressed, and therefore, the moisture absorption resistance of the inorganic SOG film 4 does not deteriorate.

Next, as shown in FIG. 5, using the resist pattern 5 as a mask, the inorganic SOG film 4 is etched by, for example, RIE using C ₂ F ₆ or CHF ₃ as a reaction gas to form a contact hole 6. Form.

Next, in the same manner as described above, an ashing process using O ₂ ions as a main reactive species is performed by a hollow cathode type ashing device shown in FIG.
And the surface layer of the inorganic SOG film 4 on the inner wall of the contact hole 6 is densified. Thereafter, cleaning is performed using an amine-based organic solvent or the like for the purpose of removing a resist residue or a polymer. At the time of this cleaning, an amine-based organic solvent or the like is applied to the inorganic SOG on the inner wall of the contact hole 6.
Although the film 4 comes into contact with the film 4, the surface layer of the inorganic SOG film 4 on the inner wall of the contact hole 6 is densified in advance by the ashing process as described above, so that the reaction of breaking the Si—H bond is suppressed, The moisture absorption resistance does not deteriorate.

Next, as shown in FIG. 8, a second wiring 7 contacting the first wiring 3 through the contact hole 6 is formed by a CVD method or a sputtering method. In most cases, heat is applied when the second wiring 7 is formed, but since the moisture absorption resistance of the inorganic SOG film 4 has not deteriorated as described above, the inorganic SOG film 4 There is no gas emission as represented, and no defects such as generation of voids in the contact hole 6 and peeling of the second wiring 7 occur.

FIG. 10, FIG. 11 and FIG.
An example of the measurement result of the infrared absorption spectrum of the film 4 is shown, and the measurement result after the application and the heat treatment of the inorganic SOG film 4, the measurement result after the ashing treatment, and the measurement result after the washing with the amine-based organic washing liquid are shown, respectively.

As can be seen from FIGS. 10, 11 and 12, the absorption peak near the wave number of 2300 cm ⁻¹ due to the Si—H bond is observed after the application and heat treatment of the inorganic SOG film 4, the ashing treatment, and the amine organic organic compound. The same is observed after washing with the washing liquid. this is,
Even after these processes, the inorganic SOG film 4
It shows that the Si—H bonds in the sample did not decrease.

As described above, according to the first embodiment,
A pressure of 40 Pa or less, for example, 1 Pa, is applied to the surface of the inorganic SOG film 4 including the Si—H bond and the inner wall of the contact hole 6.
Since the ashing process using O ₂ ions as the main reactive species is performed in an atmosphere of 3.3 Pa, the surface layer of the inorganic SOG film 4 and the surface layer of the inorganic SOG film 4 on the inner wall of the contact hole 6 are densified. be able to. For this reason, even if heat treatment or treatment with a chemical such as an amine-based organic solvent is performed later, it is possible to prevent the Si—H bonds in the inorganic SOG film 4 from being cut and reduced, and the inorganic SOG film 4 High moisture absorption resistance can be maintained. by this,
It is possible to prevent the occurrence of voids inside the contact hole 6 due to the release of gas such as moisture from the inorganic SOG film 4 and the peeling of the second wiring 7, thereby realizing a highly reliable multilayer wiring structure. can do.

Next, a second embodiment of the present invention will be described.

FIGS. 13 to 18 are sectional views showing a method of manufacturing a semiconductor device according to a second embodiment of the present invention in the order of steps.

In the method of manufacturing a semiconductor device according to the second embodiment, first, as shown in FIG. 13, an interlayer insulating film 2 is formed on a semiconductor substrate 1 similarly to the method of manufacturing a semiconductor device according to the first embodiment. An interlayer insulating film 8 is formed so as to cover the first wiring 3 formed therethrough. As the interlayer insulating film 8, an SiO ₂ film formed by a plasma CVD method using TEOS (Si (OC ₂ H ₅ ) ₄ ) as a reaction gas,
An SiO ₂ film formed by a plasma CVD method using silane (SiH ₄ ) as a reaction gas is preferably used. The interlayer insulating film 8 is formed for the purpose of protecting the inorganic SOG film 4 to be described below from a chemical solution or improving the adhesion of the inorganic SOG film 4 to a base.

Next, as shown in FIG. 14, an inorganic SOG film 4 containing a Si—H bond is spin-coated on the entire surface and then heat-treated to vitrify the inorganic SOG film 4. Next, an interlayer insulating film 9 is formed on the inorganic SOG film 4. As the interlayer insulating film 9, similarly to the interlayer insulating film 8, an SiO ₂ film or Si formed by a plasma CVD method using TEOS (Si (OC ₂ H ₅ ) ₄ ) as a reaction gas is used.
An SiO ₂ film formed by a plasma CVD method using H ₄ as a reaction gas is preferably used. This interlayer insulating film 8
Is to protect an inorganic SOG film 4 described below from a chemical solution or the like,
The second wiring 7 is formed for the purpose of improving the adhesion of the second wiring 7 to the base, which will be described later.

Next, as shown in FIG. 15, a resist pattern 5 having a predetermined shape is formed on the interlayer insulating film 9 by lithography. In this case, CVs are formed above and below the inorganic SOG film 4.
Since the interlayer insulating films 8 and 9 formed by the method D are present, it is possible to prevent a chemical solution such as a resist or a developing solution that causes a reaction for breaking the Si—H bond from coming into contact with the inorganic SOG film 4. Therefore, the moisture absorption resistance of the inorganic SOG film 4 does not deteriorate.

Next, as shown in FIG. 16, using the resist pattern 5 as a mask, the interlayer insulating film 9 and the inorganic SOG film 4 are used.
And the interlayer insulating film 8 is formed, for example, by using C ₂ F
_The contact holes 6 are formed by etching sequentially by RIE using ₆ or CHF ₃ .

Next, as shown in FIG. 17, in the same manner as in the first embodiment, an ashing process using O ₂ ions as a main reactive species is performed by a hollow cathode type ashing device shown in FIG. 5 is removed, and the surface layer of the inorganic SOG film 4 on the inner wall of the contact hole 6 is densified (the portion densified by the ashing process is indicated by “x”). This ashing process is performed at an O ₂ flow rate of 1
00SCCM, RF power 200W, pressure 13.3Pa
(≒ 0.1 Torr) for 1 minute. After this,
The cleaning is performed using a cleaning liquid such as an amine organic solvent for the purpose of removing the resist residue and the polymer. At the time of this cleaning, the cleaning liquid is applied to the inorganic SOG on the inner wall of the contact hole 6.
Even when the surface of the inorganic SOG film 4 is in contact with the film 4, the surface layer of the inorganic SOG film 4 on the inner wall is densified in advance by the ashing process as described above. No. 4 does not deteriorate in moisture absorption resistance.

Next, as shown in FIG. 18, a second wiring 7 contacting the first wiring 3 through the contact hole 6 is formed by a CVD method or a sputtering method. In most cases, when forming the second wiring 7, high temperature is applied. However, since the moisture absorption resistance of the inorganic SOG film 4 has not deteriorated as described above, the inorganic SOG film 4 typically contains moisture. As a result, no gas is released, and therefore no defects such as generation of voids in the contact hole 6 and peeling of the second wiring 7 occur.

As described above, according to the second embodiment,
An interlayer insulating film 8 is formed on and under the inorganic SOG film 4 by CVD.
By forming 9, it is possible to prevent chemicals such as a resist and a developer from coming into contact with the inorganic SOG film 4 in a later process, so that these chemicals come into contact with the inorganic SOG film 4. It is possible to prevent deterioration of the moisture absorption resistance. Further, as in the first embodiment, after the contact hole 6 is formed in the inorganic SOG film 4, the inner wall of the contact hole 6 is subjected to an ashing process using O ₂ ions as a main reactive species. 6, the surface layer of the inorganic SOG film 4 on the inner wall can be densified, and the moisture absorption resistance of the inorganic SOG film 4 can be kept high. Thereby, it is possible to prevent the occurrence of voids in the contact hole 6 and the separation of the second wiring 7 due to the release of gas such as moisture from the inorganic SOG film 4. As described above, a highly reliable multilayer wiring structure can be realized.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical concept of the present invention are possible.

For example, in the above-described first and second embodiments, the inorganic SOG film 4 containing Si—H bonds is used as the inorganic coating type insulating film containing Si—H bonds. Any material other than the inorganic SOG film 4 may be used as long as it is an inorganic insulating film containing a Si—H bond.

[0044]

As described above, according to the present invention, after forming an inorganic coating type insulating film containing Si-H bonds on a substrate, a pressure of 40 Pa is applied to the surface of the coating type insulating film.
By performing the treatment using O ₂ ions as the main reactive species in the following atmosphere, the surface layer of the coating type insulating film can be densified. Even after treatment with chemicals,
It is possible to prevent a decrease in the Si—H bond in the coating type insulating film, and to keep the moisture absorption resistance of the coating type insulating film high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method of manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 6 is a sectional view illustrating the method for manufacturing the semiconductor device according to the first embodiment of the present invention;

FIG. 7 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 8 is a sectional view for illustrating the method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating an example of a hollow cathode type ashing apparatus used for ashing processing in the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 10 is a view showing a method of manufacturing a semiconductor device according to a first embodiment of the present invention;
9 is a graph showing an example of a measurement result of an infrared absorption spectrum of a G film.

FIG. 11 shows an inorganic SOG after an ashing process in the method of manufacturing a semiconductor device according to the first embodiment of the present invention;
4 is a graph showing an example of a measurement result of an infrared absorption spectrum of a film.

FIG. 12 is a graph showing an example of a measurement result of an infrared absorption spectrum of an inorganic SOG film after cleaning with an amine-based organic cleaning liquid in the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 13 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 14 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 15 is a sectional view for illustrating the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 16 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 17 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 18 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to the second embodiment of the present invention.

FIG. 19 is a cross-sectional view for explaining a conventional method for manufacturing a semiconductor device.

FIG. 20 is a graph showing an example of a measurement result of an infrared absorption spectrum of an inorganic SOG film after application and heat treatment in a conventional method for manufacturing a semiconductor device.

FIG. 21 is a graph showing an example of a measurement result of an infrared absorption spectrum of an inorganic SOG film after cleaning with an amine-based organic cleaning liquid in a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2, 8, 9 interlayer insulating film 3 first wiring 4 inorganic SOG film 6 contact hole 7 second wiring

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-196537 (JP, A) JP-A-5-13405 (JP, A) JP-A-5-299521 (JP, A) JP-A-2- 230735 (JP, A) JP-A-57-103333 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/316 H01L 21/312

Claims (4)

(57) [Claims] After forming an inorganic coating type insulating film containing a Si—H bond on a substrate, the surface of the coating type insulating film is
A method for forming an insulating film, characterized in that a treatment using O ₂ ions as a main reactive species is performed in an atmosphere at a pressure of 40 Pa or less. 2. A pressure of 6. on the surface of the coating type insulating film.
Method for forming the insulating film according to claim 1, characterized in that as performs processing in which the O ₂ ions and the main reactant in an atmosphere of 6～13.3Pa. 3. After forming a contact hole in the coating type insulating film, a pressure of 4 is applied to an inner wall of the contact hole.
2. The method for forming an insulating film according to claim 1, wherein a treatment using O ₂ ions as a main reactive species is performed in an atmosphere of 0 Pa or less. 4. The method according to claim 3, wherein the inner wall of the contact hole is subjected to a treatment using O ₂ ions as a main reactive species in an atmosphere at a pressure of 6.6 to 13.3 Pa. A method for forming an insulating film.