JP3120471B2 - Method for manufacturing semiconductor device - 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 manufacturing a semiconductor device, and more particularly to a method for preventing oxidation of a copper wiring formed on the semiconductor device.

[0002]

2. Description of the Related Art In recent years, electrode wiring has been miniaturized in accordance with high integration of ULSI. Aluminum or an aluminum-based alloy has been frequently used as an electrode wiring material. However, as the line width of the wiring decreases, electromigration becomes severe and it becomes difficult to guarantee reliability. Therefore, refractory metals such as molybdenum (Mo) and tungsten (W) have been tried as a wiring material in place of aluminum, but the resistance is as high as twice or more that of aluminum in bulk and even higher in thin films. Therefore, a material that is resistant to electromigration and has low resistance is required. Therefore, it is conceivable to use copper (Cu) as a wiring material instead of aluminum. Copper has low resistance, is resistant to electromigration, and can be formed into fine devices.

However, the reason that copper wiring has not been applied to devices so far is that Cu is oxidized at a temperature of about 200 ° C. in an atmosphere containing even a few percent of oxygen. That is, in the wafer process, CVD
Since the Cu film is subjected to a process of exposing it to an oxygen atmosphere at a high temperature, such as formation and annealing of an insulating film by a method, there has been a problem that it is oxidized there. For example, when a SiO ₂ film is formed as an insulating film by a CVD method after the formation of Cu wiring, the wafer is exposed to a substrate temperature of 300 ° C. to 400 ° C. in, for example, SiH ₄ + N ₂ O gas. At this time, Cu is oxidized by oxygen contained in the reaction gas. When annealing is performed after the formation of the Cu wiring, the annealing is performed at 400 ° C. to 700 ° C. by flowing N ₂ in a normal electric furnace. However, a small amount of residual oxygen existing in the furnace and oxygen (O) in the SiO ₂ film Then, Cu is oxidized. Cu, unlike Al, does not form a stable oxide film on the surface, so when the surface reacts with oxygen, oxygen diffuses into the film and becomes copper oxide, the electrical resistance of which rises rapidly and is not suitable for practical use as wiring. Will be.

In the prior art disclosed in Japanese Patent Application Laid-Open No. 63-299250, silicon is deposited on a Cu wiring and heat-treated in an oxygen atmosphere to form copper-silicon dioxide (Cu-Si).
O ₂ ) alloy is used to prevent oxidation of the Cu wiring.

[0005]

[SUMMARY OF THE INVENTION However, even with such prior art, or to become a structure that contains SiO ₂ in the Cu wiring, the silicon deposited on the Cu wiring in an oxygen atmosphere heat treatment Therefore, Cu has a greater chance of reacting with oxygen and cannot completely prevent oxidation of Cu. Therefore, an effective method for preventing oxidation of Cu wiring has been demanded.

The present invention has been made in view of such conventional problems, and has as its object to obtain a method of manufacturing a semiconductor device in which oxidation of a Cu wiring is prevented.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method of etching a base substrate under the same conditions as those for etching a titanium layer and copper.
And a barrier metal layer,
A copper wiring is formed thereon, and a titanium (Ti) film is formed on the surface of the copper wiring.
Forming a, the copper wiring and a titanium film by a heat treatment
Forming a copper-titanium alloy film, and forming an insulating film containing oxygen (O) on the copper wiring on which the copper (Cu) -titanium (Ti) -based alloy film is formed. And a solution to the problem.

[0008]

The presence of the copper-titanium alloy film on the surface of the copper wiring suppresses the reaction between the insulating film (for example, SOG film, plasma SiO ₂ film, etc.) containing oxygen (O) and copper. That is, titanium (Ti) in the copper-titanium alloy film
Has an action of gettering oxygen, so that oxygen in the insulating film is combined with titanium and does not react with copper inside even after high temperature treatment.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of a method for manufacturing a semiconductor device according to the present invention will be described below with reference to embodiments shown in the drawings.

(First Embodiment) FIGS. 1 to 5 show a first embodiment of the present invention.

In this embodiment, first, an oxide film 11 made of SiO ₂ is formed on a silicon substrate (not shown) on which elements are formed, and a contact hole (not shown) is formed at a predetermined position of the oxide film 11. Open a hole. Subsequently, a titanium (Ti) film 12 as a contact metal is formed to a thickness of, for example, Å using a DC magnetron sputtering method, and then a titanium nitride (TiN) film 13 as a barrier metal is formed.
Is formed to a thickness of, for example, 1000 °.

Further, on the titanium nitride film 13, copper (C
u) The film 14 is formed to a thickness of, for example, 5000 ° using a DC magnetron sputtering method.

The copper film 14 is patterned using, for example, a reactive ion etching (RIE) method.
The etching conditions are as shown below.

O Etching gas: carbon tetrachloride (CC
l ₄ ) -80% nitrogen (N ₂ ) O Pressure 0.02 Torr O Substrate temperature 350 ° C O Etching mask Sio ₂ Under these etching conditions for the copper film 14, titanium nitride (TiN) as an underlayer is further added. Film 13, titanium (Ti) film 1
2 can be etched. After the etching, the copper film 14, the titanium nitride film 13, and the titanium film 12 are processed into a sectional shape as shown in FIG.

Next, as shown in FIG. 2, a titanium (Ti) film 15 is formed on the entire surface to a thickness of, for example, 500.degree. By using a DC magnetron sputtering method.

Thereafter, lamp annealing is performed, for example, at 450 ° C. for 60 seconds to cause the copper film 14 and the titanium film 15 to react with each other. As shown in FIG. 3, a copper-titanium alloy (CuTi _x ) film is formed around the copper film 14. 16 are formed.

Next, the unreacted titanium film 15 on the oxide film 11 is removed with ammonia peroxide to form a structure as shown in FIG.

Next, as shown in FIG. 5, S
An OG (Spin On Glass; for example, OCD-Type7 16000T manufactured by Tokyo Ohka) film 18 is spin-coated and cured at 400 ° C.

At this time, in the conventional copper wiring, a reaction between copper and SOG occurs, so that the copper is oxidized and the resistance is increased, so that the wiring is not practically used as a wiring. However, in this embodiment, the copper wiring is not oxidized by the operation described below.

The presence of the copper-titanium alloy film 16 on the surface of the copper film 14 can suppress the reaction between the insulating film containing oxygen (O) and copper. That is, since the titanium (Ti) in the copper-titanium alloy film 16 has an action of gettering oxygen, when the high-temperature heat treatment is performed, the oxygen in the insulating film is combined with the titanium and the copper in the internal copper film 14 no response.

Therefore, when an SOG film 18 is spin-coated as an insulating film and cured at 400 ° C., a copper-titanium compound and titanium oxide (TiN) are formed on the upper and side portions of the copper film 14 as shown in FIG. Since the stable layer (Cu-Ti-TiO) 17 having the mixed phase of (TiO) is formed, the internal copper film (copper wiring) 14 is not oxidized.

(Second Embodiment) This embodiment is an example in which SiO ₂ formed by a plasma CVD method is used as an insulating film containing oxygen (O) as a constituent.

First, in this embodiment, after a copper-titanium alloy film is formed on the surface of the copper film 14 in the same procedure as in the first embodiment, the SiO ₂ film 19 is formed by plasma CVD.
Is formed to a thickness of, for example, 7000 °.

The conditions for forming the SiO ₂ film 19 are as follows.

Reaction gas and its flow rate Silane (SiH ₄ ): 500 _SCCM oxygen (O ₂ ): 120 _SCCM Helium (He): 3800 _SCCM Pressure: 1.3 Torr Formation temperature: 380 ° C. _{When the second} film 19 is formed, FIG.
The cross-sectional shape as shown in FIG. Again, the first
The same effect as that of the embodiment can be obtained.

That is, the presence of the copper-titanium alloy film on the surface of the copper film 14 can suppress the reaction between SiO ₂ and copper. Since titanium (Ti) in the copper-titanium alloy film has an action of gettering oxygen, even in a high-temperature heat treatment, oxygen in SiO ₂ is combined with titanium and does not react with the internal copper film 14.

Therefore, after forming the SiO ₂ film 19 as an insulating film, a copper-titanium compound and titanium oxide (Ti) are formed on the upper and side surfaces of the copper film (copper wiring) 14 as shown in FIG.
The stable layer 17 having the mixed phase of O) is formed.

The two embodiments have been described above.
The present invention is not limited to these, but can be applied to various copper wiring structures.

[0029]

According to the present invention, titanium on a base substrate
Burr that can be etched under the same conditions as layer and copper etching
And a copper wiring on the barrier metal layer.
Forming a titanium (Ti) film on the surface of the copper wiring , and reacting the copper (wiring) film with the titanium film by heat treatment.
Forming a copper-titanium alloy film, and the copper (C
u)-forming an insulating film containing oxygen (O) on the copper wiring on which the titanium (Ti) -based alloy film is formed. The presence of the titanium-based alloy film has an effect of suppressing a reaction between copper and an insulating film containing oxygen (O) as a component. That is, since the titanium in the copper-titanium-based alloy film getster oxygen, the oxygen in the insulating film is combined with the titanium and does not react with the copper inside even after the high-temperature heat treatment. Therefore, the present invention has an effect that the copper wiring can be put to practical use as the wiring of the VLSI.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a process of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the steps of the first embodiment of the present invention.

FIG. 3 is a sectional view showing a step of the first embodiment of the present invention.

FIG. 4 is a sectional view showing a step of the first embodiment of the present invention.

FIG. 5 is a sectional view showing a step of the first embodiment of the present invention.

FIG. 6 is a sectional view of a second embodiment of the present invention.

[Explanation of symbols]

11: oxide film, 12: titanium film, 13: titanium nitride film,
14: copper film, 15: titanium film, 16: copper-titanium alloy film,
17 ... stable layer.

Claims (1)

(57) [Claims] 1. A method for etching a titanium layer and copper on an undersubstrate.
Forms a barrier metal that can be etched under the same conditions as
Forming a copper wiring on the barrier metal layer;
Forming a titanium (Ti) film on the surface , and reacting the copper wiring with the titanium film by heat treatment to form a copper film.
Forming a tungsten alloy film; and forming an insulating film containing oxygen (O) as a component on the copper wiring on which the copper (Cu) -titanium (Ti) -based alloy film is formed. A method for manufacturing a semiconductor device, comprising: