JPH07183299A - Method for forming copper wirings - Google Patents

Abstract

PURPOSE:To form fine copper wirings by embedding a copper film in a groove formed in an interlayer insulating film and etching back it. CONSTITUTION:A groove is formed on an SiO2 film 2 formed on a silicon substrate 1, and a copper film 4 is so deposited as to embed the groove. Then, chlorine plasma is formed in an etching chamber of a dry etching unit, the film 4 previously deposited in the plasma is exposed to react the film 4 with a copper chloride film 5 to a surface of the film 2. Then, the substrate 1 is transferred in a vacuum to an ashing chamber without exposing the reacted film 5 with the atmosphere, and heat treated. Then, the substrate 1 is again transferred to the etching chamber to etch back the film 5 by using a plasma by O2 gas or rare gas in the etching chamber, thereby forming copper wirings 6.

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 integrated circuit, and more particularly to a method for forming copper wiring.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor integrated circuits, electromigration of aluminum wiring and deterioration of stress migration resistance have become apparent. For this reason, conventionally, a method of improving resistance to electromigration and stress migration by adding silicon or copper to aluminum or taking a laminated structure of titanium or titanium nitride has been used (Yoshikawa et al. IEEE Transaction on Electron). Device (TRAN
SACTIONS ON ELECTRON DEVI
(CES) 1993 40, No. 2, 296).

On the other hand, copper-based materials have high migration resistance and low resistance, and are therefore regarded as promising wiring materials for next-generation semiconductor devices. A method of forming copper chloride, which is a chloride of copper, using chlorine gas has been used for dry etching of a copper film (Ohno et al., Japanese of Journal Applied Physicals (Jpn. J. Appl. Phys.) 1989). Two
Volume 8, page L1070). However, since copper chloride has a low vapor pressure, it has been etched while heating the substrate.

[0004]

However, in the above-mentioned conventional technique, a high temperature etching apparatus is required to perform the dry etching of the copper film. Since the dry etching is performed at a high temperature, the heat resistance of the photoresist becomes a problem, and an etching mask that replaces the conventional photoresist has been required. As an etching mask that replaces the photoresist, etching of a copper film using a hard mask (SiO ₂ or the like) having high heat resistance has been reported. (GC Schwartz et al. Journal of Electrochemical Society (J. Elec
trochem. Soc. ) 1983 130 Volume 17
(P. 77). However, there are problems such as an increase in the number of steps and adhesion between the hard mask and the copper film.

An object of the present invention is to form a groove in an insulating film without finely processing the copper film, deposit the copper film, and react the copper film other than the groove with the copper chloride film by using chlorine plasma. It is intended to provide a method for manufacturing a semiconductor integrated circuit using a conventional technique by etching back to form a copper wiring.

[0006]

According to the method of the present invention, first, a groove is formed in an insulating film formed on a substrate, and a copper film is deposited so as to fill the groove. Then, chlorine plasma is formed in the etching chamber using a dry etching apparatus, and the previously deposited copper film is exposed to this chlorine plasma so that the copper film reacts with the copper chloride film up to the surface of the insulating film. Then
The substrate is transferred to an ashing chamber in vacuum without exposing the reacted copper chloride film to the atmosphere, and the substrate is heat-treated there. After heat treatment is performed in the ashing chamber, the substrate is transported again into the etching chamber, and the copper chloride film is etched back using plasma of O ₂ gas or rare gas in the etching chamber to form a copper wiring. And a process.

[0007]

In the present invention, a copper film is formed so as to fill a groove to be a wiring on the interlayer insulating film, and the copper film reacts with the copper chloride film up to the surface of the interlayer insulating film by the step of exposing to chlorine gas plasma. Then, the temperature of the copper chloride film is raised by heating the substrate, and then the copper chloride film is etched back, whereby the copper film embedded in the groove becomes a wiring.

[0008]

【Example】

Embodiment 1 Next, the present invention will be described with reference to the drawings. Figure 1 (a)
8D are cross-sectional views of the semiconductor chip shown in the order of steps for explaining one embodiment of the present invention.

First, as shown in FIG. 1A, a silicon substrate 1 is thermally oxidized to form a SiO ₂ film having a thickness of about 500 nm, and then a wiring is formed at a desired position by reactive ion etching (RIE method). Forming a groove.

Next, as shown in FIG. 1B, the photoresist film 3 is peeled off, and then a copper film 4 is deposited on the entire surface by any one of the sputtering method, the vapor deposition method and the CVD method to fill the groove.

Next, as shown in FIG. 1C, the copper film 4 is exposed to chlorine plasma at room temperature to react with the copper film 4. The film thickness to be reacted is adjusted by the exposure time to chlorine plasma so that the copper chloride film 5 as a reaction product reacts to the surface of the SiO ₂ film 2.

Next, as shown in FIG. 1D, the silicon substrate 1 is transferred to an ashing chamber and heated without exposing the reacted copper chloride film 5 to the atmosphere. After heating the silicon substrate 1, the silicon substrate is again transported to the etching chamber and etched using oxygen gas or a rare gas plasma such as argon to etch back the copper chloride film 5 to form the copper wiring 6.

As described above, according to the present embodiment, the copper chloride film 5 in which the copper film is embedded in the groove formed in the SiO ₂ film 2 and reacted
Since the copper wiring 6 is formed by etching back, the fine processing of the copper film 3 is not required unlike the conventional case.

Embodiment 2 Next, the present invention will be described with reference to the drawings. Figure 2 (a)
8D are cross-sectional views of the semiconductor chip shown in the order of steps for explaining one embodiment of the present invention.

First, as shown in FIG. 2A, a silicon substrate 1 is thermally oxidized to form a SiO ₂ film 2 having a thickness of about 500 nm, and then a wiring is formed at a desired position by a reactive ion etching (RIE) method. Forming a groove.

Next, as shown in FIG. 2B, after peeling off the photoresist film 3, a titanium nitride film 7 is formed on the entire surface by a sputtering method, and then any of the sputtering method, the vapor deposition method or the CVD method is used. Copper film 4 is deposited on the entire surface to fill the groove.

Next, as shown in FIG. 2C, the copper film 4 is exposed to chlorine plasma at room temperature to react with the copper film 4. The film thickness to be reacted is adjusted by the exposure time to chlorine plasma so that the copper chloride film 5, which is a reaction product, reacts up to the surface of the titanium nitride film 7.

Next, as shown in FIG. 2D, the silicon substrate 1 is transferred to the ashing chamber and heated without exposing the reacted copper chloride film 5 to the atmosphere. After heating the silicon substrate 1, the silicon substrate is again transported to the etching chamber and is etched using oxygen gas or rare gas plasma to etch back the copper chloride film 5. Next, the titanium nitride film 7 exposed on the surface is etched back using fluorine plasma to form the copper wiring 6.

As described above, according to this embodiment, the copper wiring 6 is formed by etching back the copper chloride film 5 in which the copper film is embedded and reacted in the groove formed in the SiO ₂ film. No fine processing of 3 is required.

[0020]

As described above, according to the present invention,
By embedding a copper film in a groove processed at a desired position and reacting a copper film other than the groove with a copper chloride film to etch back, a copper wiring can be formed without performing fine processing of the copper film. Therefore, when used in the manufacturing process of a semiconductor integrated circuit, not only the manufacturing process can be simplified, but also the reliability and reliability of the manufacturing process can be improved and the device characteristics can be greatly improved. It has an effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor chip showing the process sequence for explaining an embodiment of the present invention.

2A to 2D are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.

[Explanation of symbols]

1 silicon substrate 2 SiO ₂ film 3 photoresist film 4 copper film 5 copper chloride film 6 copper wiring 7 titanium nitride film

Claims (1)

[Claims] 1. A step of forming a groove in which a wiring is formed after forming an interlayer insulating film on a substrate, and burying a copper film in the groove, and then exposing the copper film to plasma using chlorine. To form a copper chloride film, to heat the copper chloride film without exposing it to the outside air, and to form a copper wiring by etching the copper chloride film after heating and in the etching chamber. A method for forming a characteristic copper wiring.