JPH06112202A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] To provide a highly reliable method for forming a metal wiring, which has good workability, does not generate residues and corrosion, and can control the concentration of constituent substances. [Structure] A is formed on the insulating film 12 covering the surface of the semiconductor substrate 11.
An I film 13 is formed, and a Cu film is formed thereon. Next, the Cu film is converted into the Al—Cu alloy layer 14 by heat treatment. After the carbon film 15 is formed, the resist 16 is used as a mask and a metal wiring pattern is formed by etching. Next, an oxide of Cu is formed on the upper surface of the wiring pattern by ashing, and this is heat-treated in a reducing atmosphere. As a result, a wiring pattern whose composition is controlled, at least the upper surface of which is made of an Al—Cu alloy, is completed.

Description

Detailed Description of the Invention

 [Object 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 metal wiring.

[0002]

2. Description of the Related Art As semiconductor devices are becoming more highly integrated, the miniaturization and multi-layering of constituent elements are being rapidly advanced, and the production of VLSI is also being put to practical use. As a wiring material used in such a VLSI, an aluminum alloy containing aluminum as a main component has been widely used because it is easy to process and has a relatively low wiring resistance. However, with the reduction of the wiring width and the wiring film thickness and the multi-layer wiring, the reliability of the wiring is deteriorated.

Electromigration and stress migration are the causes of the decrease in the reliability of wiring.
Electromigration and stress migration are phenomena in which the force that moves aluminum atoms is the flow of electrons and mechanical stress, respectively, and the movement of aluminum atoms causes voids in the wiring and leads to disconnection. The crystal structure is closely related to the generation of voids, and the grain boundaries play a major role in the movement of atoms. An aluminum alloy containing aluminum as a main component used for wiring has a polycrystalline structure, that is, an aggregate of single crystal grains having different orientations, and has many grain boundaries. Further, the number of lattice defects and atomic vacancies is large, and the activation energy for grain boundary diffusion and surface diffusion of aluminum atoms is low. With the miniaturization and multi-layering of wiring, stress due to current density and stress applied to wiring increases, and wiring reliability is a serious problem. In addition, previous studies have shown that wiring reliability is dramatically improved by strengthening the crystal grain boundaries by alloying by adding a metal other than aluminum as a measure to reduce reliability. .
(A.J.Learn: J. Electronic M
materials. vol. 3,1974,531;
T. Hosoda et. al. : 27th Int.
Reliability Phys. Symp. , P.
202, 1989)

Conventionally, aluminum alloy wiring added with a metal other than aluminum from the beginning in order to prevent electromigration and stress migration has been used. However, wiring resistance increases due to the added metal, wiring workability deteriorates, and after processing, There are problems such as the occurrence of corrosion. Further, as a method for improving the reliability against migration of aluminum, it has been proposed to increase the grain size and increase the orientation, but if a dissimilar metal is mixed during deposition, an alloy layer is formed at the grain boundary. In this case, there arises a problem that the crystal grain size varies, or that a crystal grain having a large grain size cannot be obtained.

FIG. 3 shows a first example of a conventional process for forming an aluminum alloy wiring. First, as shown in FIG. 3A, an insulating film 32 such as a silicon oxide film is formed on a silicon substrate 31, and an aluminum-copper alloy film 33 is formed thereon by sputtering using an aluminum-copper alloy target. . Next, as shown in FIG. 3B, a resist pattern 34 is formed only on the wiring pattern to be formed. Next, as shown in FIG. 3C, the aluminum-copper alloy film 33 is etched using the resist pattern 34 as a mask to form an aluminum-copper alloy wiring 35. Next, as shown in FIG. 3D, the resist is ashed to form an aluminum-copper alloy wiring pattern 35.
However, in the wiring thus formed, corrosion 36 is generated due to the local cell effect of aluminum and copper, and etching residue 3 generated when copper serves as a mask.
There is a problem such as occurrence of 7.

Therefore, a method as shown in FIG.
152984) was proposed. First, as shown in FIG. 4A, an insulating film 42 such as a silicon oxide film is formed on a silicon substrate 41, an aluminum film is subsequently formed, and the wiring 43 is processed by etching. Next, FIG.
As shown in (b), the wiring is coated with a film 44 of a metal other than aluminum, such as copper. Next, as shown in FIG. 4C, copper is diffused from the film 44 into the aluminum wiring by heat treatment to form an aluminum-copper alloy 45. Next, after removing the excess copper 46 by fuming nitric acid, as shown in FIG.
Alloy wiring is formed as shown in FIG.

[0007]

As described above, an aluminum alloy film in which a metal other than aluminum is added from the beginning is formed by sputtering, and an aluminum alloy wiring pattern is formed by etching using a resist pattern formed by photolithography as a mask. According to the method, problems such as an increase in wiring resistance due to the added metal, deterioration of wiring workability, and occurrence of corrosion after processing occur.

Further, after the aluminum film is processed into a wiring by etching, a film of a metal other than aluminum is formed on the wiring as it is, and this is heat treated to alloy the metal other than aluminum with aluminum. According to the method, when the wiring width and shape are different, the concentration of the metal other than aluminum contained per unit volume of the wiring is different, and the composition of the wiring cannot be controlled.

The natural oxide film formed on the aluminum surface instantly forms several angstroms even at a vacuum degree of 10 ^-5 Torr and exists as a passive film. In the atmosphere, 30 to 50 angstroms are generated, and after generation, it exists stably with almost no further growth. Even if a metal other than aluminum is formed on the aluminum film with an alumina film interposed and heat-treated, this acts as a diffusion barrier to prevent alloying, and there is a problem that a wiring having a desired concentration cannot be obtained. Therefore, an object of the present invention is to provide a method for manufacturing a semiconductor device, which can surely obtain an alloy wiring having a desired composition. [Constitution of Invention]

[0010]

In order to solve the above-mentioned problems, the present invention first forms a first film containing aluminum as a first metal as a main component on a semiconductor substrate, and aluminum is formed on this film. A second film made of the second metal or a carbon film containing the second metal is formed without forming an oxide film. In this state, mutual diffusion occurs between aluminum and the second metal. Next, the first film and the second film, or the laminated film including the carbon film is patterned using a resist to form a metal wiring pattern. Next, the resist is ashed and removed in an atmosphere containing at least oxygen. Next, this semiconductor substrate is heat treated in a reducing atmosphere,
An alloy of aluminum and a second metal is formed on at least the upper surface of aluminum to complete the wiring pattern.

As the first film, other than aluminum, a film containing Cu or Ag as a main component may be formed.
An alloy film containing a metal selected from Al, Cu and Ag may be formed.

[0012]

After the wiring of the first metal containing aluminum as a main component is processed, the film of the second metal is formed on the upper surface and the side surface of the wiring, and this is heat-treated to alloy the metal other than aluminum with aluminum. In the method, the concentration of the metal other than aluminum depends on the surface area of the wiring.

For example, as shown in FIG. 5A, an aluminum wiring 53 having a constant film thickness = t and a rectangular cross section with widths a and b (a <b) is formed on the silicon substrate 51. It is assumed that the formed insulating film 52 of silicon oxide or the like is on the same substrate. Then, a copper film 54 having a thickness h is formed on this wiring pattern by vapor deposition, and heat treatment is used to diffuse all the copper in contact with the aluminum wiring into the wiring.
It is assumed that aluminum-copper alloy wiring is formed. If the copper concentration per unit wiring length is Da and Db when the width is a and when the width is b, Da = {ah + 2h (t + h)} / at, Db = {bh + 2h (t + h)} / Bt

[0014] Here, since a <b, Da>
It becomes Db. That is, when the wiring density in the same substrate is different due to the difference in wiring width and there are wirings with different wiring widths on the same substrate, the migration life varies depending on the wiring width. Therefore, the reliability of the wiring cannot be improved. Therefore, FIG.
As shown in (b), when the metal is diffused only from the upper surface of the aluminum wiring, the copper concentration in the wiring is Da = Db = h / t. Therefore, the copper concentration in the wiring is constant regardless of the width of the wiring. This applies not only to the difference in wiring width but also to the difference in wiring shape.

The present invention has been made paying attention to this point, and an alloy layer with a dissimilar metal is formed on the upper surface of the wiring, and the dissimilar metal is diffused into the wiring by heat treatment. As a result, the composition of the wiring can be accurately controlled, and a highly reliable wiring can be formed. The heat treatment atmosphere is H or C
By setting the reducing atmosphere containing O, the controllability of the concentration of the dissimilar metal can be improved.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1A to 1D are sectional views showing a manufacturing method according to a first embodiment of the present invention in the order of steps.

In this embodiment, first, as shown in FIG. 1A, the plane orientation (100) and the specific resistance are 1.0000 to 2.0.
Hydrogen burning oxidation is performed on the n-type silicon substrate 11 having a thickness of 000 Ωcm to form a silicon oxide film 12 having a thickness of 1 μm. Then, an aluminum film 13 having a thickness of 0.4 μm is formed by sputtering using an aluminum target.

As shown in FIG. 1 (b), a copper film is continuously formed by 5 angstrom sputtering without breaking the vacuum, and the copper film is kept in vacuum at 200 ° C. for 3 days.
After heat treatment for 0 sec, aluminum-50 is applied to the surface layer.
% Copper alloy layer 14 is formed. Here, in the step of forming copper, 40 sccm of argon gas was introduced into the chamber of ultimate vacuum of 10 ^-9 Torr, DC bias of -150 V was applied to the substrate, RF plasma was generated, and the surface of the aluminum film was argon gas. After removing the aluminum surface oxide film by reverse sputtering in the inside, a copper film may be formed without breaking the vacuum. Regarding the alloy of aluminum and copper, all the copper in the surface layer may be alloyed as described above, or the alloy may be formed only at the interface between aluminum and copper.

Next, a carbon film 15 is formed on the alloy layer 14 with a thickness of 0.
1 μm is formed to form a laminated film. Then, a resist pattern 16 is formed by a photoresist method, and the pattern of the carbon film 15 is formed using this as a mask.

After that, as shown in FIG. 1C, the aluminum film 1 is formed using the resist and the carbon film pattern as a mask.
3 and aluminum-50% copper alloy layer 14 are etched to form laminated wiring patterns (13 and 14). Here, regarding the etching of the aluminum-copper alloy layer 14, ions of BCl ₃ plasma or Ar plasma are used.
Physically etching (sputtering) by a known method. The carbon film 15 is the aluminum-copper alloy layer 14
Is used to obtain sputtering resistance that cannot be obtained with the resist 16. The etching of the aluminum film 13 is performed by a known method of chemically forming a chloride of Al with a chlorine-based gas and evaporating the chloride.

Next, as shown in FIG. 1D, only the resist is ashed by plasma downflow of oxygen and fluorine. With the carbon film attached, this is heat-treated at 500 ° C. for 30 seconds in a reducing atmosphere of H ₂ 10% -argon 90% in a furnace whose temperature rises and falls is ± 1000 ° C. for 1 minute, and the surface layer copper Diffused into aluminum,
Aluminum-0.5% copper alloy wiring 17 is formed. Finally, as shown in FIG. 1E, the carbon film 15 is ashed in oxygen plasma to complete the aluminum-copper alloy wiring 17. Note that, here, the aluminum-copper alloy wiring having a large grain size can be formed by performing the heat treatment with the carbon film attached.

In the present embodiment, a laminated film of carbon, aluminum-copper alloy, and aluminum is etched at once by a resist mask, and then the resist and carbon are ashed in oxygen plasma, and then hydrogen or carbon monoxide is added. Copper may be diffused by heat treatment in a reducing atmosphere containing copper. Here, the copper concentration in aluminum can be appropriately changed by controlling the film thickness of aluminum and copper and the heat treatment temperature and time. Further, when excess copper remains on the surface of aluminum, the copper can be removed by treating it in a nitric acid solution. 2A to 2D are sectional views showing a manufacturing method according to a second embodiment of the present invention in the order of steps.

In this embodiment, first, as shown in FIG. 2A, a silicon oxide film 22 is formed on a substrate 21 by the same method as that shown in FIG. 1A and is sputtered using an aluminum target. An aluminum film 23 having a film thickness of 0.4 μm is formed. As shown in FIG. 2 (b), a carbon-50% copper film is continuously formed by 10 angstrom sputtering without breaking the vacuum, and then heat treatment is performed in vacuum at 200 ° C. for 30 seconds. An aluminum-50% copper alloy layer 24 and a carbon-copper alloy layer 25 are formed on the layers.

Next, a resist pattern 26 is formed by a photoresist method, and as shown in FIG.
The laminated film of the copper alloy layer 25, the aluminum-copper alloy layer 24, and the aluminum film 23 is processed into a wiring pattern by etching. Here, regarding the etching of the carbon-copper alloy layer 25 and the aluminum-copper alloy layer 24, physical etching is performed with ions of BCl ₃ plasma or Ar plasma. The etching of the aluminum film 23 is performed with a chlorine-based gas chemically, for example, by a known method of forming and vaporizing Al chloride.

Next, as shown in FIG. 2D, the carbon in the resist 26 and the carbon-copper alloy layer 25 is ashed in oxygen plasma to form a copper oxide film 27 on the aluminum-copper alloy layer 24. Form. Finally, as shown in FIG.
₂ 10% - 450 ℃ with argon 90% in the reducing atmosphere,
A heat treatment is performed for 30 minutes to diffuse the copper of the surface layer into aluminum, and the aluminum-0.5% copper alloy wiring 28
To form.

FIG. 6 shows the concentration of copper in the aluminum wiring formed by the conventional manufacturing method shown in FIG. 4 and the manufacturing methods according to the first and second embodiments of the present invention shown in FIGS. The copper concentration in the formed aluminum wiring is plotted against the wiring width. In the figure, line A shows the wiring according to the conventional method, and
The wiring according to the method according to the embodiment is shown by a line B. In the conventional example, the copper concentration changes due to the difference in the wiring width, and the variation is large, whereas in the embodiment of the present invention, the copper concentration is constant and the variation is small regardless of the wiring width.

For example, in the first embodiment of the present invention, 0.4 μ
When copper was deposited in an amount of 0.01 μm on an aluminum film of m and the copper was diffused, an aluminum-copper alloy having a copper concentration of 0.5 wt% with respect to aluminum was produced. Under these conditions, the length is 10 m and the width is 0.5 μm.
As a result of performing a standing test at 200 ° C. for each of the aluminum wirings of m, 0.3 μm, and 0.2 μm using 100 wirings, no defects occurred even after 3000 hours. Although the n-type silicon substrate is used in both of the embodiments, the specific resistance is 4,5000 to 6,000.
A p-type silicon substrate of 0 Ωcm may be used.

Although Al is used as the first metal of the wiring in both of the above-mentioned embodiments, Cu, Ag are used instead of Al.
Can be used. Similarly, other alloys such as Al-Si alloys can be used. In addition, a barrier metal such as titanium or titanium nitride may be laid under the wiring. Further, in both of the above-mentioned Examples, Cu was used as the second metal of the wiring, but Ni, Pd, or Pt was used instead of this, and similar results were obtained. Further, in the above both Examples, the sputtering method was used as the method for forming the metal film.
A CVD method, a plating method or the like may be used. Further, the heat treatment temperature, atmosphere, time, copper concentration in the carbon film, and film thickness can be appropriately changed.

Furthermore, the resist pattern was used as a mask when etching the first film, the second curtain, and the alloy layers thereof. Even if the resist pattern recedes and disappears, the carbon film or The carbon film containing the second metal can be used as an etching mask. After removing the resist, the carbon film or the second metal may be used as an etching mask for the carbon film. In addition, the present invention can be modified and implemented in various modes without departing from the gist thereof.

[0030]

As described above, according to the present invention,
Regardless of the width and shape of the wiring, the composition of the wiring in the same substrate can be accurately controlled, and a highly reliable metal wiring can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing method according to a first embodiment of the present invention in the order of steps (a) to (e).

FIG. 2 is a sectional view showing a manufacturing method according to a second embodiment of the present invention in the order of steps (a) to (e).

FIG. 3 is a cross-sectional view showing a conventional method of forming a metal wiring in the order of steps (a) to (d).

FIG. 4 is a cross-sectional view showing another conventional method of forming a metal wiring in the order of steps (a) to (d).

FIG. 5 is a diagram for explaining the difference in operation between the conventional technique (a) and the present invention (b).

6 is a plot of the copper concentration in the aluminum wiring formed by the conventional method shown in FIG. 4 and the methods of the first and second embodiments according to the present invention shown in FIGS. The figure.

[Explanation of symbols]

11 ... Silicon substrate, 12 ... Silicon oxide film, 13 ... Aluminum film, 14 ... Aluminum-copper alloy layer, 15 ...
Carbon film, 16 ... Resist, 17 ... Aluminum-copper alloy wiring pattern, 21 ... Silicon substrate, 22 ... Silicon oxide film, 23 ... Aluminum film, 24 ... Aluminum-copper alloy layer, 25 ... Carbon-copper alloy layer, 26 ... Resist, 27
... Copper oxide film, 28 ... Aluminum-copper alloy wiring pattern.

Claims (2)

[Claims] 1. Al, Cu, and Ag on a semiconductor substrate
A first component containing a first metal selected from the group consisting of
A step of forming a film, and a step of forming a second film made of a second metal selected from the group consisting of Cu, Ni, Pd, and Pt on the first film and different from the first metal, By heat treatment, the first and second films of the first and second films are formed.
Reacting a metal to form an alloy layer of the first and second metals on the first film, forming a carbon film on the second film, and forming a resist pattern on the carbon film And a step of etching the carbon film using the resist pattern as a mask, and etching the first film, the alloy layer and the second film using the carbon film or the resist pattern as a mask to form a wiring pattern, A method of manufacturing a semiconductor device, comprising: a step of removing the resist and the carbon film in an atmosphere containing oxygen; and a step of diffusing the second metal in the alloy layer into the first film by heat treatment. 2. Al, Cu, and Ag on a semiconductor substrate
A step of forming a first film containing a first metal as a main component selected from the group consisting of Cu, Ni, Pd, and Pt, and forming the first metal on the first film. A step of forming a carbon film containing a different second metal, and a heat treatment to react the first and second metals of the first film and the carbon film to each other so that the first and second metals are formed on the first film. Forming a metal alloy layer, forming a resist pattern on the carbon film, and etching the carbon film using the resist pattern as a mask, and the alloy layer using the carbon film or the resist pattern as a mask And a step of forming a wiring pattern by etching the first film, a step of removing the resist and the carbon film in an atmosphere containing oxygen, and a step of preliminarily removing the second metal in the alloy layer by heat treatment. The method of manufacturing a semiconductor device including a step of diffusing into the first film.