JP3325714B2 - Semiconductor device and method of manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to aluminum (not limited to pure aluminum but also aluminum (Al) including aluminum alloys containing a small amount of Si or Cu and used as wiring for semiconductor devices). The present invention relates to a method of manufacturing a semiconductor device having a multilayer wiring, and more particularly to a method of manufacturing a semiconductor device characterized by a method of forming a wiring layer for making a connection between wiring layers via via holes (through holes).

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated,
Wiring also tends to be miniaturized and multilayered. In particular, as the wiring width becomes smaller and the via hole diameter becomes smaller as called the half-micron process, not only the contact holes but also the via holes formed between the wiring layers need to be completely filled with conductive material. Come up. In Al wiring, it has been proposed to fill a via hole with an Al sputtering layer.

When the lower Al wiring and the upper Al wiring are connected via via holes, the substrate is heated to a high temperature, for example, about 500 ° C. when forming the upper Al film in order to improve the filling of the via holes with Al. Al high-temperature sputtering performed by a sputtering method is considered to be good.

In order to further improve the embedding, the upper Al
In the film sputtering step, in order to improve the wettability on the lower Al film and the surface of the interlayer insulating film, titanium (Ti) is used as a wetting layer prior to the formation of the upper Al film.
It has been proposed to form a film (1992 Symposi
um on VLSI Technology of Technical Papers, 74-75 (1
992 IEEE)). According to the report, the hole diameter was 0.15μ.
It is alleged that via holes having an aspect ratio of 4.5 and an aspect ratio of 4.5 could be completely filled by Al high-temperature sputtering.

As a method of filling the contact holes with Al, there has been proposed a two-stage method in which an Al film is formed at a high temperature of 400 ° C. or more first, and then at a low temperature of 350 ° C. or less (Japanese Patent Laid-Open No. Hei 4 (1994)). -61118).

[0006]

In the high-temperature Al sputtering method in which via holes are filled with Al, a required thickness of an Al film is deposited in one step while the substrate is heated to about 500 ° C. Even in the two-stage method of filling the contact holes, the substrate is kept at a high temperature from the beginning of the film formation. However, when the temperature of the substrate is increased from the initial stage of the formation of the Al film, the reaction at the interface between titanium (Ti) and Al in the wetting layer occurs unevenly,
There is a problem in that the growth of the upper Al crystal grain boundary is deviated and the surface flatness of the upper Al film is deteriorated.

The Ti film to be formed as a wetting layer prior to the formation of the upper Al film is formed without heating the substrate. When the Ti film is formed at a low temperature, a columnar structure of Ti appears, and the upper Al film formed by the high-temperature Al sputtering method is diffused along the columnar structure on the Ti film, and defects are generated. May cause a decrease.

A first object of the present invention is to bury an upper layer Al in a via hole and to suppress diffusion of Al in the via hole to improve electromigration resistance. A second object of the present invention is to improve the flatness of the surface of the upper Al film.

[0009]

The invention of claim 1 includes a method of forming a two-layer Al wiring by the following steps. (A) a step of forming an interlayer insulating film covering the lower Al wiring and forming a via hole in the interlayer insulating film; and (B) setting the substrate temperature to 400 ° C. or higher, preferably 500 ° C. or higher, and forming Ti from above the interlayer insulating film. A step of depositing a film by a sputtering method, and (C) a step of heating the substrate from above without heating the substrate.
Depositing a film by a sputtering method, and forming an upper Al film for the upper wiring by further increasing the substrate temperature from above 400 ° C. to the melting point of Al, preferably 500 ° C. or higher, (D) A) a step of patterning the upper Al film for wiring.

In the invention of claim 2, after the Ti film is deposited in the step (B) of the claim 1 , an Al film is deposited in the step (C).
Before stacking , the method further includes a step of heat-treating the Ti film in a nitrogen atmosphere to nitride the surface of the Ti film. In the invention of claim 3 , the Ti film is deposited in the step (B) of claim 1.
After stacking, before depositing the Al film in step (C), the T
The method further includes a step of forming a titanium nitride film (hereinafter, referred to as a TiN film) on the i film and further forming a Ti film thereon to form a three-layer film of a Ti film-TiN film-Ti film. According to a fourth aspect of the present invention, there is provided a semiconductor device manufactured by the manufacturing method of the third aspect, wherein the lowermost layer is a Ti film between the lower Al wiring and the upper Al wiring in the via hole, the TiN film is formed thereon, and the TiN film is formed thereon. T
A three-layer film of an i film is formed.

[0011]

According to the first aspect of the present invention, since the Ti film of the wetting layer is formed with the substrate kept at a high temperature, the columnar structure of the Ti film is eliminated, and the Ti film becomes the Al film of the upper Al film.
It acts as a diffusion barrier layer and improves electromigration resistance. Further, the deposition of the upper Al film by sputtering is performed at an initial film formation at a low temperature, and thereafter,
By heating the substrate to a high temperature and depositing an Al film until a required film thickness is reached, the non-uniformity of the reaction between Ti and Al in the initial stage of film formation is suppressed, and the surface flatness of the upper Al film is improved.

According to the second aspect of the present invention, after the Ti film of the wetting layer is deposited by the sputtering method, the surface is nitrided to thereby obtain the nitrided Ti film.
The film works more effectively as a barrier layer of the upper Al film, and further improves the electromigration resistance. At this time, Ti film is deposited at a high temperature in the same manner as 請 Motomeko 1.

In the invention of claim 4 manufactured according to claim 3, a film having a three-layer structure of a Ti film-TiN film-Ti film is formed between the lower Al film and the upper Al film. The lowermost Ti film serves to reduce the contact resistance by reducing the natural oxide film Al ₂ O ₃ on the lower Al wiring. Second layer Ti
The N film functions as an Al diffusion barrier layer of the upper Al film and improves electromigration resistance. The uppermost Ti film improves the adhesion to the upper Al film, and improves the via hole filling property by the upper Al film.

[0014]

FIG. 1 shows an embodiment according to the present invention. (A) A lower Al layer is formed on a silicon substrate on which a semiconductor device such as a MOS transistor or a bipolar transistor is formed.
The substrate on which the wiring 2 is formed is used as a base. A PSG film or a BPSG film is formed as an interlayer insulating film 4 on the wiring 2.
Then, the interlayer insulating film 4 is formed by photolithography and etching.
Then, a via hole 6 is formed.

(B) A Ti film 8 is formed on the entire surface of the interlayer insulating film 4.
Is deposited to a thickness of 500 to 3000 ° by a sputtering method while heating the substrate temperature to 400 ° C. or higher, preferably 500 ° C. or higher. The substrate temperature is adjusted by blowing heated argon gas from the lower surface of the substrate or by heating with a heater. The upper limit of the substrate temperature is determined not by the Ti film formation but by the heating device. Heating to about 600 ° C. is possible.

(C) From the top of the Ti film 8, A
1 is deposited by a sputtering method. Al film 1
0 is deposited by a two-stage sputtering method. In the first step, the substrate is deposited to a thickness of 500 to 3000 ° without heating the substrate. Thereafter, the substrate is heated to 400 to 600 ° C., preferably 500 to 600 ° C., and is kept for 1 to 2 minutes until the substrate temperature is stabilized. Deposit the film. The second-stage Al film has a thickness equal to or greater than that of the first-stage Al film, and is adjusted to a thickness that completely fills the via hole. The substrate temperature is lower than the melting point of Al (about 660 ° C.). The upper limit of the substrate temperature determined by the heating device is generally equal to or lower than the melting point of Al. Thereafter, the Al film 10 is patterned by photolithography and etching to form an upper Al wiring.

FIG. 2 shows an embodiment according to the second aspect of the present invention. (A) As in FIG. 1, an interlayer insulating film 4 is formed on a lower Al wiring 2 and a via hole 6 is formed. (B) A Ti film 8 is formed on the interlayer insulating film 4 by a sputtering method. The Ti film 8 is formed while heating the substrate temperature to 400 to 600 ° C., preferably 500 to 600 ° C. as in FIG.

(C) RTA (Rapi) in a nitrogen atmosphere
d Thermal Annealing) treatment, or by heating with a heater, T
An iN layer 20 is formed. (D) An Al film 10 is formed on the TiN layer 20 by a two-step sputtering method as in FIG. Thereafter, the Al film 10 is patterned by photolithography and etching to form an upper Al wiring.

FIG. 3 shows an embodiment according to the third aspect. (A) As in FIG. 1, an interlayer insulating film 4 is formed on a lower wiring 2 and a via hole 6 is formed. (B) The Ti film 30 is formed on the interlayer insulating film 4 by 300 to 100
It is formed to a thickness of 0 ° by a sputtering method.

(C) On the Ti film 30, a TiN film 32 is formed to a thickness of 500 to 1500 ° by a reactive sputtering method. (D) A Ti film 34 is formed on the TiN film 32 by 500 to 1500.
It is formed to a thickness of Å by a sputtering method.

(E) An Al film 10 for upper wiring is formed on the Ti film 34 by a two-step sputtering method as in FIG. Thereafter, the Al film 10 is patterned by photolithography and etching to form an upper Al wiring.

In the embodiment shown in FIG.
The sputtering process for forming the N film 32 and the Ti film 34 is performed by heating the substrate to preferably 400 ° C. or higher, more preferably 500 ° C. or higher. Also, the TiN film 32
May be obtained by nitriding the surface of the Ti film by heat treatment in a nitrogen atmosphere instead of the reactive sputtering method.

Although the embodiment shows the step of forming a two-layered Al wiring, in the case of further forming a multi-layered wiring, the wiring formed by the upper Al film 10 in the embodiment shown in FIGS. By repeating the steps of FIGS. 1 to 3 thereon, a multilayer wiring can be further formed.

[0024]

According to the first aspect of the present invention, the Ti film of the wetting layer is formed with the substrate kept at a high temperature.
The columnar structure of the i film is eliminated, and the Ti film functions as a barrier layer for Al diffusion of the upper Al film, thereby improving electromigration resistance. In addition, the upper Al film is deposited by sputtering at an initial film formation temperature at a low temperature, and thereafter, the substrate is heated to a high temperature to deposit an Al film until a required film thickness is obtained. The unevenness of the Al reaction is suppressed to improve the flatness of the surface of the upper Al film. According to the second aspect of the present invention, the T
After the i-film is deposited by the sputtering method, the surface is nitrided, whereby the Ti film whose surface is nitrided functions more effectively as a barrier layer of the upper Al film, and the electromigration resistance is further improved.

According to the third and fourth aspects of the present invention, since the three-layer film composed of the Ti film, the TiN film and the Ti film is formed between the lower Al film and the upper Al film, the lowermost layer is formed. The natural oxide film Al ₂ O ₃ on the lower Al wiring is reduced by the Ti film to reduce the contact resistance, and the upper layer A is formed by the second TiN film.
1 prevents the Al film from diffusing, thereby improving the electromigration resistance, improving the adhesion with the upper Al film by the uppermost Ti film, and improving the via hole filling property by the upper Al film.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing an embodiment corresponding to claim 1;

FIG. 2 is a process sectional view showing an embodiment corresponding to claim 2;

FIG. 3 is a process sectional view showing an embodiment corresponding to claim 3;

[Explanation of symbols]

 Reference Signs List 2 lower Al wiring 4 interlayer insulating film 6 via hole 8, 30, 34 Ti film 10 upper Al film 20 TiN layer 32 TiN film

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01L 21/3205 H01L 21/321 H01L 21/3213 H01L 21/768

Claims (4)

(57) [Claims] 1. A method for manufacturing a semiconductor device, comprising a method for forming a multilayer wiring including a two-layer aluminum wiring formed by the following steps. (A) a step of forming an interlayer insulating film covering the lower aluminum wiring and forming a via hole in the interlayer insulating film; and (B) a step of setting the substrate temperature to 400 ° C. or higher and forming the via hole on the interlayer insulating film.
Depositing a titanium film by sputtering process, (C) a temperature in the range of depositing by sputtering an aluminum film in a state where the substrate is not heated thereon, the further 400 ° C. The substrate temperature thereon to the melting point of aluminum And deposit aluminum film by sputtering method
And depositing an upper aluminum film for the upper wiring, a step of patterning the wiring of (D) the upper aluminum film. 2. After depositing a titanium film in the step (B) and before depositing an aluminum film in the step (C),
2. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of heat-treating the titanium film in a nitrogen atmosphere to nitride a surface of the titanium film. 3. After depositing a titanium film in the step (B) and before depositing an aluminum film in the step (C),
2. The method for manufacturing a semiconductor device according to claim 1, further comprising a step of forming a titanium nitride film on said titanium film and further forming a titanium film thereon. 4. The lower aluminum wiring and the upper aluminum wiring are insulated by an interlayer insulating film,
In a semiconductor device having a multilayer wiring including at least a two-layer wiring in which predetermined portions of a lower aluminum wiring and an upper aluminum wiring are connected via a via hole in the interlayer insulating film, a lower layer and a lower layer in the via hole The lowermost layer is a titanium film between the aluminum wiring and the upper aluminum wiring,
A titanium nitride film is formed thereon, and a titanium film is further formed thereon. A three-layer film is formed by depositing the lowermost titanium film by sputtering at a substrate temperature of 400 ° C. or higher. A semiconductor device, comprising: