JP2001274246A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) Abstract: A thin film containing SiO ₂ as a main component (S) capable of oxidizing and protecting Cu wiring and suppressing an increase in parasitic capacitance between wirings.
iO ₂ thin film). After forming a SiN thin film on a Cu wiring, a heat treatment is performed in an atmosphere containing oxidizing species and reducing species. According to such a heat treatment, oxidation of Cu in the Cu wiring 14 can be prevented by the reducing species, and Si in the SiN thin film 15 can be thermally oxidized by the oxidizing species. As a result, C
The dense SiO ₂ thin film 16 that can protect the
It can be selectively formed on the surface of the wiring 14. SiO ₂ is Si
A lower dielectric constant than the ₃ N _4. Therefore, the increase in the parasitic capacitance between the wirings can be suppressed by the SiO ₂ thin film 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor device characterized by a method for forming an insulating film used for protection of Cu wiring and insulation between wirings, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, as a wiring of an LSI requiring particularly high performance and high speed operation, a wiring mainly composed of Cu (Cu
Wiring) is often used. Since the Cu wiring has a lower resistance than the conventionally used wiring mainly composed of Al (Al wiring), R
There are advantages that the C delay can be suppressed, and that disconnection is difficult even when the current density is high.

After forming the wiring, an insulating film covering the surface of the wiring is formed for the purpose of protecting the wiring and insulating between the wirings. As this type of insulating film, there are generally a deposited insulating film mainly composed of SiO ₂ , a deposited insulating film mainly composed of Si ₃ N ₄ , and a coated insulating film mainly composed of SiO ₂ or an organic material. .

Considering the case where an insulating film covering the surface of the Cu wiring is formed, the oxidation rate of Cu is very high, so that the Cu wiring is oxidized. Deposited insulating films cannot be used. Therefore,
A deposited insulating film containing SiO ₂ as a main component, such as a SiO ₂ film formed by a CVD method, cannot be used.

On the other hand, a deposited insulating film accompanied by a heat treatment in a reducing atmosphere during film formation, for example, SiH ₄ , SiH ₂
CVD using a reducing gas such as Cl ₂ or NH ₃ as a raw material
The Si ₃ N ₄ film formed by the method can be used as an insulating film covering the surface of the Cu wiring. However, this kind of deposited insulating film is generally excellent in denseness and chemical resistance, but has a problem that parasitic capacitance becomes large because of a higher dielectric constant than SiO ₂ .

On the other hand, a coating insulating film containing SiO ₂ or an organic material as a main component has a dielectric constant of 3 or less, which is lower than 3.9 of SiO ₂ , so that the parasitic capacitance can be reduced. In addition, there is an advantage that it can be formed at a low temperature. However, since this type of coated insulating film has low density, it is liable to be deteriorated by ashing for removing the resist or various chemical treatments, and there is a problem in protection of wiring. Therefore, when a coating insulating film is used, it is necessary to reinforce the insulating film in combination with another insulating film.

[0007]

As described above, after the wiring is formed, an insulating film covering the surface of the wiring is formed for the purpose of protecting the wiring and insulating between the wirings. As this type of insulating film, a deposited insulating film containing SiO ₂ as a main component, Si
A deposited insulating film mainly containing ₃ N ₄ and a coated insulating film mainly containing SiO ₂ or an organic material are known. But C
In the case of u wiring, these insulating films have problems in oxidation of Cu wiring, increase in parasitic capacitance between wirings, or protection of Cu wiring.

The present invention has been made in view of the above circumstances, and has as its object to form an insulating film capable of oxidizing and protecting Cu wiring and suppressing an increase in parasitic capacitance between wirings. It is an object of the present invention to provide a method of manufacturing a semiconductor device which can be performed.

[0009]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, typical ones are briefly described as follows.

In other words, in order to achieve the above object, in a semiconductor device according to the present invention, a step of forming a first insulating film having a wiring groove on a surface, and covering an inner wall of the wiring groove with a barrier metal film. A step of forming a wiring containing Cu as a main component inside the wiring groove, a step of forming a film containing Si and N on a region including a surface of the wiring, and including an oxidizing species and a reducing species The heat treatment in the atmosphere reduces Cu in the conductive film and the constituent material of the barrier metal film, and oxidizes Si in the film containing Si and N, thereby forming SiO on the surface of the wiring. Forming a second insulating film containing ₂ as a main component. It is preferable that the oxidizing species and the reducing species have a predetermined partial pressure ratio as described in the embodiment of the invention.

With such a structure, an insulating film mainly composed of SiO ₂ can be formed on the surface of the Cu wiring without oxidizing the surface of the wiring mainly composed of Cu (Cu wiring). . Since the insulating film mainly composed of SiO ₂ is formed by heat treatment (thermal oxidation) in an atmosphere containing oxidizing species and reducing species, it is different from a coated insulating film mainly composed of SiO ₂ or the like, and is dense. Film.

Therefore, the insulating film containing SiO ₂ as a main component of the present invention is an effective insulating film for protecting the Cu wiring. Further, since SiO ₂ is a main component, Si ₃
The dielectric constant is lower than that of the N ₄ film, and an increase in parasitic capacitance between wirings can be suppressed.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0014]

Embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 11 is a process sectional view illustrating the method for manufacturing the semiconductor device according to the embodiment.

First, as shown in FIG. 1A, a thin film (SiN thin film) 2 containing Si and N is formed on the surface of a Cu film 1 as a Cu wiring.

N in the SiN thin film 2 has an effect of suppressing the formation of silicide due to the reaction between Cu and Si in the subsequent heat treatment for forming SiO ₂ . It is desirable that the thickness of the SiN thin film 2 is not less than 5 nm and not more than 50 nm. The method of forming the SiN thin film 2 is CV
Any of the D method and the PVD method may be used.

The composition of the SiN thin film 2 is a normal composition Si ₃ N
It is more desirable that Si is richer than ₄ . For that purpose, for example, a method of depositing by a sputtering method using a sputtering gas in which N ₂ is added to an Si target and Ar is effective. Further, 45% of Si ₂ Cl ₆ and NH ₃ are used as raw materials.
A method of depositing at a temperature of 0 ° C. by a low pressure CVD method is also effective.

Next, as shown in FIG. 1B, H ₂ O and H
_By heat treatment at about 450 ° C in a mixed atmosphere of ₂ ,
The Si in the SiN thin film 2 is oxidized to change the thin film 2 into a thin film (SiO ₂ thin film) 3 containing SiO ₂ as a main component.

At this time, the surface of the Cu film 1 is protected by the SiN thin film 2 or the oxidized SiN thin film 2. Therefore, the surface of the Cu film 1 is not oxidized. Further, since N in the SiN thin film 2 forms an Si—N bond at the interface between the Cu film 1 and the SiN thin film 2, the progress of the silicide reaction on the surface of the Cu film 1 can be suppressed. As a result, the SiO ₂ thin film 3 can be formed on the surface of the Cu film 1 without oxidizing the surface of the Cu film 1.

At a certain partial pressure ratio, the mixed gas of H ₂ O and H ₂ acts as a reducing gas for Cu,
Works as an oxidizing gas. Such partial pressure ratio range, thermodynamic between H ₂ O and partial pressure ratio of H ₂ in which the Cu ₂ O and SiO ₂ are each a stable oxide is formed by calculating the (P _H2O / P _H2) It can be known by estimating the lower limit.

Table 1 shows the lower limit of the partial pressure ratio (P _H2O / P _H2 ).

[0023]

[Table 1]

From the table, when the temperature of the atmosphere is 427 ° C.,
If 1 × 10 ⁻¹³ ≦ P _H2O / P _H2 ≦ 1 × 10 ⁷ , C
It can be seen that Si in the SiN thin film 2 can be selectively oxidized without oxidizing the u film 1.

The atmosphere in which such oxidation can be performed is H ₂ O
The present invention is not limited to a mixed atmosphere of H ₂ and H ₂ , and can be performed in a mixed atmosphere of CO ₂ and CO, for example. In this case, for example, at 427 ° C., 1 × 10 ⁻¹² ≦ P _CO2 / P _CO ≦ 1
If it is × 10 ⁸ , the Cu film 1 is not oxidized and the SiN thin film 2
The Si inside can be selectively oxidized.

If a radical is used as an oxidizing species, Si in the SiN thin film 2 can be selectively oxidized at a lower temperature. For example, if two types of radicals, OH ^* and H ^* , are used, heat treatment at a temperature of about 250 ° C.
Si in the iN thin film 2 can be selectively oxidized.

Thereafter, as shown in FIG.
A step of forming an interlayer insulating film 4 containing SiO ₂ as a main component on the O ₂ thin film 3 according to a well-known method follows.

As described above, according to the present embodiment, C
without oxidizing the surface of the Cu film 1 as a u-wiring,
It is possible to form the SiO ₂ film 3 on the surface. Since the SiO ₂ thin film 3 is formed by heat treatment (thermal oxidation) in a mixed atmosphere of H ₂ O and H ₂ , the SiO ₂ thin film 3 is a dense film unlike a coating insulating film mainly composed of SiO ₂ or the like. .

Therefore, the SiO ₂ thin film 3 is an effective insulating film for protecting the Cu film 1 as Cu wiring. Further, since the SiO ₂ thin film 3 is an insulating film containing SiO ₂ as a main component, the SiO ₂ thin film 3 has a lower dielectric constant than the Si ₃ N ₄ film and can suppress an increase in parasitic capacitance between wirings. As a result, the reliability of the Cu wiring can be increased, and the signal delay can be reduced.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
FIG. 11 is a process sectional view illustrating the method for manufacturing the semiconductor device according to the embodiment.

FIG. 2A shows a state in which after forming an interlayer insulating film 11 mainly composed of SiO ₂ on a silicon substrate (not shown), a wiring groove 12 is formed on the surface of the interlayer insulating film 11. FIG.

Next, as shown in FIG.
A barrier metal film 13 is deposited on the entire surface so as to cover the inner wall. In the case of Cu wiring, the material of the barrier metal film 13 is TaN, WN, VN, NbN, CrN, Mo.
Nitrides such as N are preferred. A film other than the nitride film can be used as long as it prevents Cu from diffusing into the interlayer insulating film 11 and has good adhesion to the interlayer insulating film 11 and the Cu wiring.

Next, as shown in FIG.
Is formed over the entire surface so as to completely bury the inside of the substrate. In order to form a Cu film 14 having a good buried shape, a CVD method or a plating method may be used for the film formation.

When the plating method is used, it is preferable to form a thin Cu film as a seed layer on the surface of the barrier metal film 13 before forming the Cu film 14. The thin Cu film is formed by, for example, a PVD method. By forming the seed layer, a Cu film 14 having a better shape can be formed.

When a film forming method in which a film is isotropically deposited like a CVD method is used, the thickness of the wiring groove 12 is reduced by setting the thickness of the Cu film 14 to a half or more of the width of the wiring groove 12. The inside can be completely buried with the Cu film 14.

Next, as shown in FIG.
emical Mechanical Polishing) to form wiring grooves 1
Unnecessary Cu film 14 outside 2 is removed, and the surface is planarized to form Cu wiring 14.

The Cu wiring 14 is a so-called single damascene wiring, and is connected to a lower metal wiring on a silicon substrate (not shown) via a plug (not shown). Further, the present invention can be applied to the case of dual damascene wiring. In the case of dual damascene wiring, the wiring groove 12 may be replaced with a via hole and a wiring groove.

Next, as shown in FIG. 2E, a thin film (SiN thin film) 15 containing Si and N is formed on the interlayer insulating film 11 and the Cu wiring 14.

N in the SiN thin film 15 has an effect of suppressing the formation of silicide due to the reaction between Cu and Si in the subsequent heat treatment for forming SiO ₂ . It is desirable that the thickness of the SiN thin film 15 is not less than 5 nm and not more than 50 nm. The method for forming the SiN thin film 15 is as follows.
Any of a CVD method, a PVD method, and a sputtering method may be used.

The composition of the SiN thin film 15 is a normal composition Si ₃
Desirably, it is Si-rich than N ₄ . For this purpose, for example, a method in which a Si target is deposited by a sputtering method using a gas obtained by adding N ₂ to Ar is effective. Also,
It is also effective to deposit Si ₂ Cl ₆ and NH ₃ as raw materials at a temperature of 450 ° C. by a low pressure CVD method.

Next, as shown in FIG. 2 (f), H ₂ O and H
_By heat treatment at about 450 ° C in a mixed atmosphere of ₂ ,
The Si in the SiN thin film 15 is oxidized to convert the SiN thin film 15 into Si.
Change to a thin film (SiO ₂ thin film) 16 containing O ₂ as a main component.

At this time, the surface of the Cu wiring 14 is
It is protected by the thin film 15 or the oxidized SiN thin film 15. Therefore, the surface of the Cu wiring 14 is not oxidized. Also, N in the SiN thin film 15 causes Cu
Since a Si—N bond is formed at the interface between the film 1 and the SiN thin film 15, the progress of the silicide reaction on the surface of the Cu wiring 14 can be suppressed. As a result, the SiO ₂ thin film 15 is formed on the surface of the Cu wiring 15 without oxidizing the surface of the Cu wiring 15.
Can be formed.

If the range of the partial pressure ratio between H ₂ O and H ₂ is the same as that of the first embodiment, only Si can be selectively oxidized without oxidizing Cu. In the embodiment, since the barrier metal film 13 exists,
It is necessary that the conditions be such that the barrier metal film 13 is not oxidized.

As a desirable material of the barrier metal film 13,
All of the above are less susceptible to oxidation than Si.
It is a nitride of a material (an oxide is unstable). Sand
Chi, H _TwoO and H_TwoBy adjusting the partial pressure ratio of
Without oxidizing the ametal film 13 and the Cu wiring 14,
SiO_TwoOnly the thin film 16 can be selectively oxidized
You.

For example, as the barrier metal film 13, TaN
When a film is used, the temperature of the atmosphere is 427 ° C. and 1 × 10
^-13 ≤P _H2O / P _H2 ≤1 × 10-10 Then, the Si in the SiN thin film 15 can be selectively oxidized without oxidizing the Cu wiring 14.

A similar effect can be obtained by using a mixed gas of CO ₂ and CO. When OH ^* and H ^* are used, the Si in the SiN thin film 15 can be selectively oxidized at a lower temperature. Can be.

Next, as shown in FIG. 2G, an interlayer insulating film 17 mainly composed of SiO ₂ is formed on the SiO ₂ thin film 16. Thereafter, according to the method described above, a required number of further upper-layer Cu wirings are formed. Also, Cu wiring 1
Even when the metal wiring (not shown) below layer 4 is a Cu wiring, it is preferable that the Cu wiring is also formed according to the above-described method.

As described above, according to the present embodiment, C
The SiO ₂ thin film 16 can be selectively formed on the surface of the Cu wiring 14 without oxidizing the surfaces of the u wiring 14 and the barrier metal film 13. This SiO ₂ thin film 16 is made of H ₂
Since it is formed by heat treatment (thermal oxidation) in a mixed atmosphere of O and H ₂ , it is a dense film, unlike a coating insulating film mainly composed of SiO ₂ or the like.

Therefore, the SiO ₂ thin film 16 is an effective insulating film for protecting the Cu wiring 16. Furthermore, Si
Since O ₂ is a main component, the dielectric constant is lower than that of the Si ₃ N ₄ film, and an increase in parasitic capacitance between wirings can be suppressed. As a result, the reliability of the Cu wiring can be increased, and the signal delay can be reduced.

The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. For example, the Cu film does not need to be a pure Cu film, but may be, for example, a CuAl alloy film containing Al. That is, the main component may be Cu.

In the second embodiment, the Cu wiring 14
Has been described in contact with the underlying metal wiring, but the present invention is also effective when contacting with an impurity diffusion layer on the substrate surface such as a source / drain diffusion layer.

As a semiconductor substrate, an SOI substrate may be used in addition to a normal silicon substrate in order to reduce a parasitic capacitance and produce a higher-speed device. Also,
A semiconductor substrate whose active region is made of SiGe may be used.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0054]

As described in detail above, according to the present invention, C
A film containing Si and N is formed on the surface of a wiring mainly composed of u (Cu wiring), and then a heat treatment is performed in an atmosphere containing oxidizing species and reducing species, thereby protecting the Cu wiring and forming the wiring. An insulating film capable of suppressing an increase in parasitic capacitance therebetween can be formed.

[Brief description of the drawings]

FIG. 1 is a process sectional view illustrating a method for manufacturing a semiconductor device according to a first embodiment of the present invention;

FIG. 2 is a process sectional view illustrating a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Cu film (conductive film) 2 Thin film containing Si and N 3 Thin film containing SiO ₂ as a main component 4 Interlayer insulating film 11 Interlayer insulating film (first insulating film) 12 Wiring groove 13 Barrier Metal film 14: Cu film (conductive film) as Cu wiring 15: Thin film containing Si and N 16: Thin film containing SiO ₂ as a main component (second insulating film) 17: Interlayer insulating film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kyoichi Suguro 8th Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Toshiba Yokohama Office 5F033 HH11 HH32 HH34 JJ01 JJ11 JJ32 JJ34 KK11 KK32 KK34 MM01 MM02 MM12 MM12 MM13 NN06 NN07 PP06 PP14 PP26 QQ48 QQ74 QQ76 RR04 RR06 RR20 SS01 SS02 SS07 SS09 SS11 SS13 TT02 XX20 XX24 XX28 5F058 BC02 BC08 BF04 BF24 BF30 BH03 BJ02

Claims (5)

[Claims] 1. A step of forming a conductive film containing Cu as a main component, a step of forming a film containing Si and N on the surface of the conductive film, and a heat treatment in an atmosphere containing oxidizing species and reducing species. Forming an insulating film mainly composed of SiO ₂ on the surface of the conductive film by reducing Cu in the conductive film and oxidizing Si in the film containing Si and N. And a method for manufacturing a semiconductor device. 2. A step of forming a first insulating film having a wiring groove on a surface, a step of covering an inner wall of the wiring groove with a barrier metal film, and a wiring containing Cu as a main component inside the wiring groove. Forming a film containing Si and N on a region including the surface of the wiring; and performing heat treatment in an atmosphere containing an oxidizing species and a reducing species to form Cu and the barrier in the conductive film. Forming a second insulating film containing SiO2 as a main component on the surface of the wiring by reducing the constituent material of the metal film and oxidizing Si in the film containing Si and N. A method for manufacturing a semiconductor device, comprising: 3. The semiconductor device according to claim 1, wherein the film containing Si and N is formed by a low pressure CVD method using Si ₂ Cl ₆ and NH ₃ as source gases. Manufacturing method. 4. A combination of the oxidizing species and the reducing species,
H ₂ O and H ₂ , CO ₂ and CO, or OH radical and H
2. A combination of radicals.
A method for manufacturing a semiconductor device according to claim 2. 5. The material according to claim 2, wherein the constituent material of said barrier metal film is Ta nitride, Nb nitride, V nitride, W nitride, Mo nitride or Cr nitride. A method for manufacturing a semiconductor device.