JPH08335579A - Silicon-based oxide film containing fluorine and its preparation - Google Patents

Abstract

PURPOSE: To reduce dielectric constant while maintaining reliability by securing heat resistance of a silicon-based oxide film containing fluorine. CONSTITUTION: Nitrogen atoms are contained in a silicon-based oxide film containing fluorine, and the concentration of the nitrogen atoms contained in the film is 0.1-5 atomic %. In its manufacturing method, raw material gases comprising a silane-based gas, a gas containing fluorine, and an oxide dinitrogen gas are used for example. Or a raw material gas containing at least a silane- based gas and oxygen, a gas containing fluorine, and ammonia gas are used. Or a chemical vapor phase growth method using a raw material gases containing at least a silane-based gas, a gas containing oxygen, a gas containing fluorine, and a nitrogen gas are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low dielectric constant fluorine-containing silicon oxide film used as an interlayer insulating film in a method for manufacturing a semiconductor device and a method for manufacturing the same, and particularly to a design rule of 0.25 μm or less. The present invention relates to a silicon oxide film containing fluorine used in the device process according to 1. and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the demand for miniaturization of semiconductor devices, low power consumption, high speed, etc., reduction of the dielectric constant of an interlayer insulating film has been studied as one of the means for realizing them. The currently disclosed low dielectric constant materials have a low dielectric constant by containing carbon atoms or fluorine atoms. At present, a material having a dielectric constant of about 1.5 to 2.5 has been realized.

In a low dielectric constant material containing carbon atoms, organic S
OG (SOG is an abbreviation for Spin on glass), polyimide, polyparaxylylene and the like are known. It is said that these materials have a low dielectric constant by containing a carbon atom as an alkyl group to reduce the density of the material and reduce the polarizability of the molecule itself. Further, these materials not only have a low dielectric constant, but also have heat resistance which is indispensable as a material for semiconductor devices. The organic SOG has a siloxane structure, the polyimide has an imide bond, and the polyparaxylylene has a benzene ring, so that each has heat resistance.

As a low dielectric constant material containing a fluorine atom, a silicon oxide film containing fluorine (hereinafter referred to as a SiOF film) is known. This material is silicon-oxygen-silicon (S
By terminating the (i-O-Si) bond with a fluorine (F) atom, the dielectric constant is lowered due to a decrease in density and a low polarizability of fluorine itself. This SiOF film has the highest reliability such as heat resistance and plasma resistance among low dielectric constant films.

[0005]

However, the above S
The iOF film has a dielectric constant of about 3.0 to 3.5, which is higher than that of other low dielectric constant films. That is, doping the silicon oxide film with fluorine has the effect of suppressing the occurrence of ionic polarization of the silicon oxide film and lowering the dielectric constant. However, as the doping amount of fluorine is increased, the dielectric constant starts to increase. This phenomenon is due to an increase in fluorine atoms that cannot covalently bond with silicon atoms. That is, since fluorine has a high electronegativity, it acts as an ion to increase the ionic polarizability. Therefore, S
The dielectric constant of the iOF film is only about 3.0 to 3.5.

It is an object of the present invention to provide a silicon oxide film containing fluorine and a method of manufacturing the same, which has a low dielectric constant while maintaining the reliability of the SiOF film.

[0007]

SUMMARY OF THE INVENTION The present invention is a fluorine-containing silicon oxide film and a method for manufacturing the same, which have been made to achieve the above object.

That is, the silicon oxide film containing fluorine is one in which nitrogen atoms are contained in the film.

The method for producing a fluorine-containing silicon oxide film is based on a chemical vapor deposition method, and the source gas used at that time is a source gas for forming a fluorine-containing silicon oxide film and a nitrogen atom. A gas containing is used.

[0010]

In the above fluorine-containing silicon oxide film, since nitrogen atoms are contained in the film, the nitrogen atoms covalently bond with the fluorine atoms to reduce the number of fluorine atoms acting as ions. As a result, the ionicity of the fluorine atom is lost, and the occurrence of ionic polarization is suppressed.
Therefore, the dielectric constant becomes lower.

In the above-described method for producing a silicon oxide film containing fluorine, a chemical vapor deposition method is used in which a source gas containing a source gas for forming a silicon oxide film containing fluorine and a gas containing nitrogen atoms is used. Therefore, by the vapor phase growth reaction, nitrogen atoms are separated from the gas containing nitrogen atoms, and the film is formed in a state in which the nitrogen atoms are taken into the silicon oxide film containing fluorine. The nitrogen atom then covalently bonds with the fluorine atom to reduce the number of fluorine atoms acting as ions. As a result, the ionicity of the fluorine atom is lost, and the occurrence of ionic polarization is suppressed.

[0012]

EXAMPLE A silicon oxide film containing fluorine (hereinafter referred to as a SiOF film) of the present invention is a film in which nitrogen atoms are contained in a SiOF film. The concentration of nitrogen atoms contained in this SiOF film is 0.1 atomic% or more and 5 atomic
The concentration is within the range of c% or less.

Next, the dielectric constant of the SiOF film and SiOF
The relationship with the concentration of nitrogen atoms in the film will be described with reference to FIG. The figure shows the dependence of the nitrogen atom concentration on the dielectric constant of the SiOF film, which was examined by including nitrogen atoms in a SiOF film having a dielectric constant of about 3 in the state of not containing nitrogen atoms. And the vertical axis of the figure shows the dielectric constant of the SiOF film,
The horizontal axis represents the nitrogen atom concentration in the SiOF film.

As shown in the figure, the nitrogen atom concentration-dielectric constant curve 1 has a nitrogen atom concentration of 1.0 atomic% to 2 atom.
mic% range (in the figure, the nitrogen atom concentration is 1.5 atom)
ic%) has a minimum value. On the other hand, if the nitrogen atom concentration exceeds 5 atomic%, the dielectric constant value (= 3.0) of the SiOF film containing no nitrogen atom will be exceeded. This is silicon-nitrogen-silicon (Si-
This is because N-Si) bonds are formed and the density of the silicon oxide film increases. On the other hand, the nitrogen atom concentration is 0.1a
If it is less than tomic%, the number of nitrogen atoms that can covalently bond with a fluorine atom is not sufficient, so that the number of fluorine atoms that cannot covalently bond with a silicon atom cannot be sufficiently reduced. Therefore, the fluorine atom having high electronegativity acts as an ion to increase the ionic polarizability. Therefore, the concentration of nitrogen atoms should be 0.1 atomic% or more 5
It was set to be atomic% or less.

Next, a first embodiment of the method for producing a SiOF film containing nitrogen atoms of the present invention will be described. In the first embodiment,
Monosilane (SiH ₄ ) and tetrafluoromethane (CF ₄ ) are used as source gases for forming a silicon oxide film containing at least fluorine, and dinitrogen oxide (N ₂ O) is used as a gas containing nitrogen atoms. , Chemical vapor deposition (hereinafter, referred to as CVD, CVD is a chemical vapor deposition
(abbreviation of sition) method, a SiOF film containing nitrogen atoms was formed.

An apparatus for carrying out the above CVD method is, for example, an electron cyclotron resonance (hereinafter, referred to as ECR, ECR
Is an abbreviation for Electron Cycrotron Resonance) CVD equipment. The film forming condition is that the flow rate is 3 in the source gas.
0 sccm [sccm is a volumetric flow rate (cm ³ ) per minute in a standard state] monosilane and a flow rate of 5
00 sccm of nitrous oxide and a flow rate of 10 sccm of tetrafluoromethane were used. Also, the substrate temperature is 400
C., the pressure of the vapor growth atmosphere was set to 1 Pa, the substrate bias power was set to 1 kW, and the source power was set to 3 kW. As a result of forming the SiOF film containing nitrogen atoms under the above conditions,
A nitrogen atom was contained in the F film at about 2 atomic% and a SiOF film having a dielectric constant of 2.5 was obtained.

In the first embodiment, nitrous oxide is used as the gas containing nitrogen atoms. Therefore, in the first embodiment, the nitrous oxide gas is indispensable, so it is necessary to contain at least the raw material gas. On the other hand, when the volumetric flow rate ratio of nitrous oxide gas to silane-based gas in the standard state exceeds 0.1, SiOF formed by deposition is formed.
The concentration of nitrogen atoms in the film exceeds 5 atomic%. Therefore, the dielectric constant value (= 3.0) of the SiOF film containing no nitrogen atoms is exceeded. In such a state in which a large number of nitrogen atoms are contained, a silicon-nitrogen-silicon (Si-N-Si) bond is formed and the density of the SiOF film is increased. Therefore, the volumetric flow rate ratio of the nitrous oxide gas to the silane-based gas in the standard state is 0.1.
It is necessary to: In the vapor phase growth reaction, the nitrous oxide gas is decomposed into nitrogen and oxygen. Since this oxygen acts as an oxidizing agent for silicon, no gas other than nitrous oxide is contained in the raw material gas, which contains oxygen as an oxidizing agent.

In the first embodiment, monosilane is used as the raw material gas for forming the SiOF film. For example, polysilane which is a silane-based gas [eg disilane (Si ₂ H ₆ ), trisilane (Si ₃ H _{3 8} ) etc.] can also be used. As the gas containing fluorine, a fluorocarbon-based gas [eg, hexafluoroethane (C ₂ F ₆ ), perfluoropropane (C ₃ F ₈ ), etc.] may be used instead of tetrafluoromethane. The flow rate when the gas is used may be the same as that described in the first embodiment.

Next, a second embodiment of the method for producing a SiOF film containing nitrogen atoms of the present invention will be described. In the second embodiment,
One kind of silane-based gas, monosilane, is used as a source gas for forming a SiOF film containing nitrogen atoms, oxygen (O ₂ ) is used as a gas containing oxygen, tetrafluoromethane is used as a gas containing fluorine, and ammonia (gas is used as a gas containing nitrogen). NH ₃₎ was used. Then, a SiOF film containing nitrogen atoms was formed by the CVD method.

As an apparatus for carrying out the CVD method of the second embodiment, for example, an ECRCVD apparatus was used. As film forming conditions, the raw material gases are monosilane with a flow rate of 30 sccm, oxygen with a flow rate of 300 sccm, and a flow rate of 1 sc
cm ammonia and tetrafluoromethane with a flow rate of 10 sccm were used. Further, the substrate temperature is 400 ° C., the vapor growth atmosphere pressure is 1 Pa, and the substrate bias power is 1 k.
W and source power were set to 3 kW. As a result of forming the SiOF film containing nitrogen atoms under the above conditions, a SiOF film containing nitrogen atoms of about 2 atomic% and a dielectric constant of 2.5 was obtained.

In the second embodiment described above, monosilane was used as the raw material gas for forming the SiOF film, but it is also possible to use polysilane (for example, disilane, trisilane, etc.) which is a silane-based gas, for example. It is also possible to use nitrous oxide instead of oxygen as the gas containing oxygen. As the fluorine-containing gas, a fluorocarbon-based gas (eg, hexafluoroethane, perfluoropropane, etc.) can be used instead of tetrafluoromethane.

In the second embodiment, since the source gas for forming the SiOF film and the ammonia are supplied, the ammonia gas is decomposed in the chemical vapor deposition reaction,
The film is formed in a state where nitrogen atoms are incorporated in the SiOF film. The nitrogen atom covalently bonds with the fluorine atom to reduce the number of fluorine atoms acting as ions. as a result,
The ionicity of the fluorine atom is lost, and the occurrence of ionic polarization is suppressed. Therefore, the SiOF film containing nitrogen atoms formed by the method of the second embodiment has a smaller dielectric constant than the SiOF film containing no nitrogen atoms.

Next, a third embodiment of the method for producing a SiOF film containing nitrogen atoms of the present invention will be described. In the third embodiment,
One type of silane-based gas, monosilane, was used as a source gas for forming the SiOF film containing nitrogen atoms, oxygen was used as a gas containing oxygen, and tetrafluoromethane and nitrogen (N ₂ ) were used as a gas containing fluorine. Then, a SiOF film containing nitrogen atoms was formed by the CVD method.

As an apparatus for carrying out the CVD method of the third embodiment, for example, an ECRCVD apparatus was used. As film forming conditions, the raw material gases are monosilane with a flow rate of 30 sccm, oxygen with a flow rate of 300 sccm, and a flow rate of 500.
Sccm nitrogen and a flow rate of 10 sccm tetrafluoromethane were used. Further, the substrate temperature is 400 ° C., the vapor growth atmosphere pressure is 1 Pa, and the substrate bias power is 1 k.
W and source power were set to 3 kW. As a result of forming the SiOF film containing nitrogen atoms under the above conditions, nitrogen atoms are contained at about 2 atomic% and the dielectric constant is 2.5.
A film was obtained.

In the second embodiment described above, monosilane is used as the source gas for forming the SiOF film, but it is also possible to use polysilane (for example, disilane, trisilane, etc.) which is a silane-based gas. It is also possible to use nitrous oxide instead of oxygen as the gas containing oxygen. Further, as a gas containing fluorine, instead of tetrafluoromethane, a fluorocarbon-based gas (eg hexafluoroethane, perfluoropropane, etc.)
It is also possible to use.

In the second embodiment, since nitrogen is supplied to the raw material gas for forming the SiOF film, the nitrogen gas is decomposed in the vapor phase growth reaction and nitrogen atoms are taken into the SiOF film. Be filmed. The nitrogen atom covalently bonds with the fluorine atom to reduce the number of fluorine atoms acting as ions. As a result, the ionicity of the fluorine atom is lost, and the occurrence of ionic polarization is suppressed.
Therefore, the SiOF film containing nitrogen atoms formed according to the third embodiment has a smaller dielectric constant than the SiOF film containing no nitrogen atoms.

Next, an application example of the SiOF film containing nitrogen atoms formed by the first to third embodiments will be described with reference to the schematic sectional view of the structure of FIG.

As shown in the figure, a silicon oxide film 12 is formed on the surface of a silicon substrate 11, and a plurality of aluminum wirings 13 are arranged on the silicon oxide film 12. Then, by any one of the methods described in the first to third embodiments, SiOF containing nitrogen atoms is formed in a state of covering the wirings 13 and in a state of filling the space between the wirings 13.
The film 14 is formed. After that, the silicon oxide film 15 is formed by a normal CVD method. The SiOF film 14 containing nitrogen atoms formed as described above had a dielectric constant of 2.5. The concentration of nitrogen atoms contained in the SiOF film 14 containing nitrogen atoms was 2 atomic%. Thus, Si containing nitrogen atoms with a dielectric constant of 2.5 between the wirings 13
Since the OF film 14 is formed, it is possible to form a semiconductor device having a small inter-wiring capacitance. Moreover, the SiOF film 14 containing nitrogen atoms is excellent in reliability such as heat resistance and plasma resistance because the silicon-based oxide film is a basic material.

[0029]

As described above, according to the silicon oxide film containing fluorine of the present invention, since the silicon oxide film containing fluorine contains nitrogen atoms, the nitrogen atoms are covalently bonded to the fluorine atoms. Thus, the number of fluorine atoms acting as ions can be reduced. Therefore, the ionicity of the fluorine atom can be eliminated, and the occurrence of ionic polarization can be suppressed. Therefore, the SiOF film has a lower dielectric constant than the conventional SiOF film. Moreover, since the SiOF film containing nitrogen atoms is basically made of a silicon oxide film, reliability such as heat resistance and plasma resistance can be ensured.

In the above-mentioned method for producing a fluorine-containing silicon oxide film, a chemical vapor deposition method is used in which a source gas for forming a fluorine-containing silicon oxide film and a nitrogen atom-containing gas are used as source gases. Therefore, the silicon-based oxide film containing fluorine can be formed in the state containing nitrogen atoms by the vapor phase growth reaction.

[Brief description of drawings]

FIG. 1 is a relationship diagram between a dielectric constant of a SiOF film and a nitrogen atom concentration.

FIG. 2 is a schematic configuration sectional view of an application example.

[Explanation of symbols]

 1 Nitrogen atom concentration-dielectric constant curve

Claims (6)

[Claims] 1. A silicon oxide film containing fluorine, wherein the silicon oxide film containing fluorine contains nitrogen atoms. 2. The silicon-containing oxide film containing fluorine according to claim 1, wherein the concentration of nitrogen atoms contained in the silicon-containing oxide film containing fluorine is 0.1 atomic% or more and 5 atomic.
% Or less, a silicon oxide film containing fluorine. 3. A method for manufacturing a silicon oxide film containing fluorine by a chemical vapor deposition method, wherein a source gas used in the chemical vapor deposition method forms a silicon oxide film containing at least fluorine. A method for producing a silicon-containing oxide film containing fluorine, characterized in that it comprises a raw material gas for carrying out the above and a gas containing nitrogen atoms. 4. The method for producing a silicon-containing oxide film containing fluorine according to claim 3, wherein the raw material gas comprises a silane-based gas, a fluorine-containing gas, and nitrous oxide gas. A method for producing a silicon oxide film containing fluorine, wherein the gas contains at least dinitrogen oxide gas, and the volumetric flow rate ratio of the dinitrogen oxide gas to the silane gas in the standard state is 0.1 or less. 5. The method for producing a silicon oxide film containing fluorine according to claim 3, wherein the source gas contains at least a silane gas, a gas containing oxygen, a gas containing fluorine, and an ammonia gas. A method of manufacturing a silicon oxide film containing fluorine. 6. The method for producing a silicon oxide film containing fluorine according to claim 3, wherein the raw material gas contains at least a silane gas, a gas containing oxygen, a gas containing fluorine, and a nitrogen gas. A method of manufacturing a silicon oxide film containing fluorine.