JPH05136137A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method for a semiconductor device wherein the diffusion amount of dissimilar metal into metal wiring is made constant in dependent of wiring width, make concentration optimum, and improve the reliability of the metal wiring. CONSTITUTION:On a silicon substrate in which elements are formed, a silicon oxide film 2 is formed, on which an Al wiring 3 is patterned and formed. In the state that a TiN film 4 turning to a diffusion barrier is selectively formed on the side wall of the Al wiring 3, a Cu film 5 is formed, and Cu is diffused from only the upper surface of the Al wiring 3, thereby forming an Al wiring 7 which contains Cu.

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 forming a metal wiring layer.

[0002]

2. Description of the Related Art Al or Al alloy has been widely used as a wiring material for semiconductor devices. This is because the Al film and the Al alloy film are excellent in terms of film forming workability, low resistance, low resistance contact with the substrate semiconductor, and adhesion with the insulating film.

However, with the high integration of integrated circuits, as the Al wiring width becomes smaller and the current density increases, the reliability of the Al wiring such as electromigration and stress migration becomes a big problem.

It has been already known that it is effective to contain Cu which is a barrier of Al diffusion in the Al wiring against this problem. The simplest method of containing Cu in the Al wiring is to prepare an Al target containing Cu, form a film by a sputtering method, and perform patterning. However, this method has a problem that the workability is worse than that of a pure Al film.

Therefore, a method has been considered in which after forming an Al wiring pattern, Cu is added to this. FIG. 7 shows the method. After a silicon oxide film 62 is formed on a silicon substrate 61 on which elements have been formed and necessary contact holes (not shown) are formed, an Al wiring 63 containing no Cu is formed thereon by a normal process (see FIG. 7 (a)
). Then, a Cu film 64 is formed on the Al wiring 63 (FIG. 7 (b)). Then, heat treatment is performed to remove Cu from Al.
A Cu diffusion layer (reaction layer) is formed on the surface of the wiring layer by diffusing it into the wiring 63. (Fig. 7 (b)). Then unreacted Cu
After removing the film, heat treatment in forming gas,
A Cu-containing Al wiring 66 in which Cu is uniformly diffused in the Al wiring is obtained (FIG. 7 (c)).

According to this method, the good workability of the Al wiring is maintained, but a new problem arises. C in Al wiring
This is a phenomenon in which the u concentration changes depending on the wiring width.
For example, FIG. 8 shows the wiring width dependence of the Cu concentration in the Al wiring when a 0.5 nm Cu film is deposited on a 400 nm thick Al wiring and heat-treated. As shown in the figure, the Cu concentration in the wiring increases as the wiring width decreases. This phenomenon is such that the Cu diffusion amount from the Al wiring upper surface changes depending on the wiring width, whereas the Cu diffusion amount from the side surface does not depend on the wiring width and is constant as long as the film thickness is constant. Because of. That is, as the wiring width becomes narrower, the ratio of the diffusion amount from the side surface to the total amount of Cu in the Al wiring increases.

This phenomenon means that the Cu concentration cannot be optimized at the same time for many Al wirings having different widths in the integrated circuit. More specifically, when the Cu concentration is optimized for a certain wiring width, if the wiring width is smaller than this, the Cu concentration becomes too high. If the Cu concentration becomes too high, the A
The l ₂ Cu layer (θ layer) is deposited. This Al ₂ Cu precipitate layer acts as a large diffusion barrier against the atomic flow of Al, and voids are formed downstream of the atomic flow, causing disconnection.
Further, the θ layer deposited on the grain boundary suppresses the subsequent grain growth of Al. Therefore, although the crystal grain size of Al is desired to be large, the crystal grain size of Al becomes large at most about 2 to 3 μm. Since the crystal grain size varies even within the same film, there are many crystal grains with a grain size of 1 μm or less, which hinders the realization of a bamboo structure in which large crystal grains are connected.

[0008]

As described above, in the conventional method of forming Cu having high migration resistance and diffusing Cu in the wiring after Al wiring patterning,
There is a problem that the Cu concentration depends on the wiring width, which lowers the reliability of the wiring.

The present invention has been made in consideration of such circumstances, and the diffusion amount of the dissimilar metal into the metal wiring is made constant regardless of the wiring width, and the concentration thereof is optimized to improve the reliability of the metal wiring. Another object of the present invention is to provide a method for manufacturing a semiconductor device.

[0010]

According to the present invention, a wiring pattern made of a first metal film is formed on a semiconductor substrate on which an element is formed, with a diffusion barrier film selectively formed on a side wall,
After that, a second metal film different from the first metal film is formed,
It is characterized in that heat treatment is performed so that only the upper surface of the first metal film reacts with the second metal film. Either the step of forming the wiring pattern using the first metal film or the step of forming the diffusion barrier layer on the side wall thereof may be performed first.

[0011]

According to the present invention, the second metal is diffused from the upper surface of the first metal film wiring only, so that the diffusion concentration of the second metal in the wiring is constant regardless of the wiring width. Therefore, the concentration of the second metal can be optimized for all the wirings on the element chip, and a highly reliable metal wiring can be obtained.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a metal wiring forming process of a semiconductor device according to a first embodiment of the present invention. A desired element is formed on the silicon substrate 1, and the surface thereof is covered with the silicon oxide film 2. After a necessary contact hole (not shown) is formed in the silicon oxide film 2, an Al wiring 3 is formed (FIG. 1 (a)). The Al wiring 3 is formed by a known method such as film formation by sputtering and patterning by photolithography. The film thickness of the Al wiring 3 is, eg, 400 nm. After the Al wiring 3 is formed in this way,
Heat treatment is performed in a forming gas at 450 ° C. for 15 minutes using a diffusion furnace. As a result, the grain size of Al grows.

Thereafter, a TiN film 4 is formed with a thickness of, for example, about 50 nm (FIG. 1 (b)). The TiN film 4 is then etched by reactive ion etching (RIE),
l It is left only on the side wall of the wiring 3 (Fig. 1 (c)). This Ti
The N film 4 is used as a diffusion barrier layer in the subsequent step of diffusing Cu into the Al wiring.

Then, the natural oxide film formed on the surface of the Al wiring 3 is removed by the reverse sputtering method, and then the Cu film 5 of 0.5 nm, for example, is formed by the sputtering method (FIG. 1).
(d)). Ar in a diffusion furnace with the Cu film 5 formed
A heat treatment is carried out in gas at 250 ° C. for 15 minutes, whereby a reaction layer (Cu diffusion layer) 6 of Al and Cu is formed on the surface of the Al wiring 3 (FIG. 1 (e)). The side surface of the Al wiring 3 is protected by the TiN film 4 so that it does not react with Cu.

After that, the substrate is dipped in nitric acid,
The unreacted Cu film is removed. Finally, heat treatment at 400 ° C. for 15 minutes is performed in a forming gas in a diffusion furnace to remove Cu.
Al wiring 7 is obtained in which all are diffused (Fig. 1 (f)
).

As described above, in this embodiment, Cu diffusion is performed only on the upper surface of the patterned Al wiring. Therefore, the Cu concentration in the Al wiring is constant regardless of the wiring width.
Wiring is obtained.

FIG. 2 shows a metal wiring forming process for a semiconductor device according to the second embodiment of the present invention. The parts corresponding to those in the first embodiment are designated by the same reference numerals as those in the first embodiment. A desired element is formed on the silicon substrate 1, and the surface thereof is covered with the silicon oxide film 2. After the necessary contact holes are formed in the silicon oxide film 2, the Ti / TiN laminated film 8 is formed by the sputtering method. The laminated film 8 has, for example, a laminated structure of a Ti film 30 nm and a TiN film 80 nm.
The laminated film 8 has a function of preventing Cu from diffusing into the substrate 1 through the oxide film 2 in the subsequent thermal process when the Cu film is formed on the laminated film 8. This Ti / TiN laminated film 8
An Al wiring 3 is formed on the Al wiring 3 (FIG. 2 (a)). Al wiring 3
The film thickness is 400 nm, for example.

Thereafter, a TiN film 4 used as a diffusion barrier layer for the Al wiring 3 is formed with a thickness of, for example, about 50 nm (FIG. 2 (b)). The TiN film 4 is etched by reactive ion etching (RIE) and left only on the side wall of the Al wiring 3 (FIG. 2 (c)).

Then, the natural oxide film formed on the surface of the Al wiring 3 is removed by the reverse sputtering method, and then the Cu film 5 of, for example, 0.5 nm is formed by the sputtering method (FIG. 2).
(d)). 20 in Ar gas with Cu film 5 formed
A heat treatment is performed for 3 minutes at 0 ° C., whereby a reaction layer 6 of Al and Cu is formed on the surface of the Al wiring 3 (FIG. 2 (e)).
). The side surface of the Al wiring 3 is protected by the TiN film 4 so that it does not react with Cu.

Then, the substrate is dipped in nitric acid,
The unreacted Cu film is removed. Further, the Ti / TiN laminated film 8 in the area other than the wiring portion is removed by RIE. Finally, heat treatment is performed at 400 ° C. for 15 minutes in the forming gas to obtain an Al wiring 7 in which Cu is diffused throughout (FIG. 2 (f)). Also in this embodiment, the same effect as the previous embodiment can be obtained.

FIG. 3 shows a metal wiring forming process for a semiconductor device according to a third embodiment of the present invention. This embodiment is a slightly modified embodiment of the second embodiment. Silicon substrate 1
A desired element is formed on the substrate, and the surface thereof is covered with the silicon oxide film 2. After the necessary contact holes are formed in the silicon oxide film 2, Ti / T is formed as in the second embodiment.
The iN laminated film 8 is formed by the sputtering method. This Ti / T
The Al wiring 3 is formed on the iN laminated film 8 (FIG. 3A).
). The film thickness of the Al wiring 3 is, eg, 400 nm.

After that, Ti used as a diffusion barrier layer
The N film 4 is formed with a thickness of, for example, about 50 nm (FIG. 3 (b)). This TiN film 4 is etched by reactive ion etching (RIE) and left only on the side wall of the Al wiring 3 (FIG. 3 (c)).

Then, the natural oxide film formed on the surface of the Al wiring 3 is removed by the reverse sputtering method, and then the Cu film 5 of 1 nm, for example, is formed by the sputtering method (FIG. 3 (d)).
). 100 in Ar gas with Cu film 5 formed
A heat treatment is performed at 10 ° C. for 10 minutes, whereby a reaction layer 6 of Al and Cu is formed on the surface of the Al wiring 3 (FIG. 3).
(e)). The side surface of the Al wiring 3 is protected by the TiN film 4 so that it does not react with Cu.

Then, the substrate is dipped in nitric acid,
The unreacted Cu film is removed. Furthermore, by chemical dry etching (CDE), the T
The i / TiN laminated film 8 and the TiN film 4 on the side wall of the wiring are removed. Finally, in forming gas, 400 ℃, 15
The heat treatment is performed for a minute to obtain an Al wiring 7 in which Cu is diffused throughout (FIG. 2 (f)). Also in this embodiment, the same effect as the previous embodiment can be obtained.

FIG. 4 shows a metal wiring forming process for a semiconductor device according to a fourth embodiment of the present invention. A desired element is formed on the silicon substrate 1, and the surface thereof is covered with the silicon oxide film 2. After the necessary contact holes are formed in the silicon oxide film 2, Al wiring 3 is formed (FIG. 4 (a)).
). The film thickness of the Al wiring 3 is, eg, 400 nm. After the Al wiring 3 is formed in this manner, heat treatment is performed in forming gas at 450 ° C. for 15 minutes. This gives A
l grain size grows.

Thereafter, an Al ₂ O ₃ film 10 having a thickness of about 10 nm is formed on the surface of the Al wiring 3 by the anodic oxidation method (FIG. 4 (b)). The Al ₂ O ₃ film 10 is anisotropically etched by ordinary RIE and left only on the side wall of the Al wiring 3 (FIG. 4 (c)).

Then, the natural oxide film formed on the surface of the Al wiring 3 is removed by the reverse sputtering method, and then the Cu film 5 of, for example, 0.5 nm is formed by the sputtering method (FIG. 4).
(d)). 25 in Ar gas with Cu film 5 formed
A heat treatment is performed at 0 ° C. for 10 minutes, whereby a reaction layer 6 of Al and Cu is formed on the surface of the Al wiring 3 (FIG. 4).
(e)).

After that, by immersing the substrate in nitric acid,
The unreacted Cu film is removed. Finally, heat treatment is performed at 400 ° C. for 15 minutes in the forming gas to obtain an Al wiring 7 in which Cu is diffused throughout (FIG. 4 (f)). Also in this embodiment, the same effect as the previous embodiment can be obtained.

FIG. 5 shows a metal wiring forming process according to the fifth embodiment of the present invention. In the examples so far, the diffusion barrier layer was formed on the side wall of the Al wiring after the Al wiring was formed.
In this embodiment, the diffusion barrier layer is formed before forming the Al wiring layer.

A desired element is formed on the silicon substrate 1, and the surface thereof is covered with the silicon oxide film 2. Necessary contact holes are formed in the silicon oxide film 2, and apart from this, a trench 11 slightly wider than the wiring width is formed in the silicon oxide film 2 along the wiring region (FIG. 5 (a)). ..
The depth of the groove 11 is 40 nm, for example. Then Ti / T
The iN laminated film 12 is formed by the sputtering method.
The l film 30 is formed by the sputtering method (FIG. 5 (b)).
The Ti / TiN laminated film 12 is formed of, for example, a Ti film of 20 nm and Ti.
The N film has a laminated structure of 60 nm, and the Al film 30 is, for example, 400
nm.

Thereafter, the Al film 3 is fluidized and flattened by heat treatment at 600 ° C. for 30 minutes. Then, the Al film 30 outside the groove is removed by etching back, whereby the Al wiring 3 is patterned only in the groove 11. (Fig. 5 (c)).

Then, the natural oxide film formed on the surface of the Al wiring 3 is removed by the reverse sputtering method, and then the Cu film 5 of 1 nm, for example, is formed by the sputtering method (FIG. 5 (d)).
). 200 in Ar gas with Cu film 5 formed
A heat treatment is carried out at 3 ° C. for 3 minutes to form a reaction layer 6 of Al and Cu on the surface of the Al wiring 3 (FIG. 5 (e)).
).

Then, the substrate is dipped in nitric acid,
The unreacted Cu film is removed. Furthermore, by chemical dry etching (CDE), the T
The i / TiN laminated film 8 is removed. Finally, heat treatment is performed at 400 ° C. for 15 minutes in the forming gas to obtain an Al wiring 7 in which Cu is diffused throughout (FIG. 5 (f)). In this embodiment, Ti / formed before the Al wiring 3 is formed
The TiN laminated film 12 acts as a barrier layer against Cu diffusion from the side wall of the Al wiring 3.

FIG. 6 shows a metal wiring forming process according to the sixth embodiment of the present invention. This embodiment is the same as the embodiment of FIG. 5 except that the Ti / Ti N laminated film 12 in the embodiment of FIG. 5 is omitted. That is, in this embodiment,
Only the silicon oxide film 2 is also used as a diffusion barrier layer for the Al wiring 3. If the diffusion of Cu into the substrate 1 through the silicon oxide film 2 is not so large as to affect the device characteristics, this embodiment can also obtain the same effect as the previous embodiment.

The present invention is not limited to the above embodiment. For example, in the embodiment, Al is used as the first metal film material which is the wiring material and Cu is used as the second metal film material to be diffused therein. However, Al is used as the first metal film material in addition to Al alloy, Cu, β-Ti, Au, Ag, etc. are used, and as the second metal film material, in addition to Cu, Cr, Ti, Z
r and the like are used, and these can be appropriately combined. Also as the barrier diffusion layer, TiN, A described in the embodiment is used.
In addition to l ₂ O ₃ and SiO ₂ , SiN or the like can be used. As the film forming method, in addition to the sputtering method and the CVD method,
The cluster ion beam method, MBE method or the like is used.
As the heat treatment method, besides heating by a diffusion furnace, lamp heating, laser annealing, electron beam annealing and the like can be used.
Others The present invention can be variously modified and implemented without departing from the spirit thereof.

[0037]

As described above, according to the present invention, the diffusion amount of a dissimilar metal into a metal wiring is made constant regardless of the wiring width and the concentration is optimized to improve the reliability of the metal wiring. The device can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a wiring forming process of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a wiring forming process of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a wiring forming process of a semiconductor device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a wiring forming process of a semiconductor device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a wiring forming process of a semiconductor device according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a wiring forming process of a semiconductor device according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a wiring forming process by a conventional method.

FIG. 8 is a diagram showing the wiring width dependency of the Cu concentration of the Cu-containing Al wiring by the conventional method.

[Description of Reference Signs] 1 ... Silicon substrate, 2 ... Silicon oxide film, 3 ... Al wiring, 4 ... TiN film (diffusion barrier layer), 5 ... Cu film, 6 ... Reaction layer, 7 ... Cu-containing Al wiring, 8 ... Ti / TiN laminated film, 10 ... Al ₂ O ₃ film (diffusion barrier layer), 11 ... Groove, 12 ... Ti / TiN film (diffusion barrier layer).

Claims (1)

[Claims] 1. A step of patterning a wiring by a first metal film on a semiconductor substrate on which an element is formed, a step of selectively forming a diffusion barrier film on a sidewall of the wiring, and a step of forming the diffusion barrier layer. A second metal film different from the first metal film is formed on the surface of the formed wiring, and heat treatment is performed to form a first metal film.
And a step of reacting the second metal film with the second metal film.