JPH04286323A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain the manufacturing method for a semiconductor device containing a metal wiring having excellent electromigration-resisting and stressmigration-resisting characteristics. CONSTITUTION:An element containing a diffusion layer 2 is formed on a silicon substrate 1, the element is covered by an insulating film 3, a contact hole is perforated, and after a TiN film 4 having the orientation of (100) has been formed, an Al film 5 is formed. As a result, the Al film 5 can be formed in the state wherein the crystal grains 6 in orientation (111) have low density. Subsequently, the crystal grains 6 of (111) are grown by conducting a heat treatment, and a polycrystalline Al film 7 of large grain diameter is formed. This Al film 7 is patterned, and a wiring is formed.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having highly reliable metal wiring.

0002

2. Description of the Related Art High density and high speed semiconductor integrated circuits have been achieved primarily by miniaturization of elements. One of the issues that has become a major issue as devices become smaller is the reliability of metal wiring. Failure occurrence modes in miniaturized metal wiring in semiconductor devices can be broadly divided into two types. One is electromigration and the other is stress migration.

Electromigration is a defect that occurs due to increased current density in metal interconnects. As the width of metal wiring becomes finer, the current density in the wiring tends to become higher and higher. The lifespan of wiring due to electromigration failure is proportional to the square of the current density, so for example, if the wiring width is reduced to 1/2 without changing the film thickness, the current density will double and the wiring life will be reduced to 1/4. It will drop to .

Stress migration is a creep failure mode that occurs due to tensile stress being applied to wiring. The tensile stress is caused by the difference in thermal expansion coefficient between the insulating film for protecting the wiring and the wiring metal, and this also tends to increase as the wiring width becomes finer. In the case of Al wiring, which is often used as wiring in semiconductor devices, when the wiring width is reduced to 1/2, the applied stress almost doubles. Since the wiring life due to this stress migration is proportional to the n-th power of the wiring width, miniaturization of the wiring width causes a significant reduction in the wiring life.

Conventionally, Al wiring has been widely used for wiring in semiconductor devices because it has excellent properties such as ease of film formation and processing, low resistance, and ease of forming contact with substrate silicon. It is. However, because of its low melting point, Al 2 wiring has low activation energy for atomic movement, and has low resistance to the above-mentioned electromigration and stress migration.

[0006] Several countermeasures have been proposed to deal with the deterioration in reliability of Al wiring due to the miniaturization of elements. Typical examples include Cu, Ti, Mg in Al.
, Hf, B, and other additives to form alloy wiring. Recently, laminated metal interconnections have been made in which a so-called barrier metal film such as TiN, TiW, etc. is provided under the Al film. Further, a laser annealing method, a rapid thermal annealing method, a high temperature bias sputtering film forming method, etc., which increase the size of the particles in the Al film, have also been proposed.

These measures to improve the reliability of Al wiring have been effective to some extent. However, the wiring width is 0.5μ
In future integrated circuits that will be
As the current density of wiring increases further, conventional reliability measures will no longer be sufficient.

[0008]

[Problems to be Solved by the Invention] As described above, migration resistance of metal wiring has become a major problem in semiconductor devices whose elements are becoming increasingly finer.

An object of the present invention is to provide a method for manufacturing a semiconductor device having highly reliable metal wiring with improved migration resistance.

[Configuration of the invention]

[0011]

[Means for Solving the Problems] A first method of the present invention includes:
After an element is formed on a semiconductor substrate, covered with an insulating film, and a contact hole is formed, a metal film is formed thereon with a low density of crystal grains having a crystal orientation of (111). Then, this metal film is heat-treated to form a polycrystalline metal film in which (111)-oriented crystal grains are grown to a large extent, and this is patterned to form wiring.

The second method of the present invention is to form a desired element on a semiconductor substrate, cover it with an insulating film and make a contact hole, and then deposit a metal film thereon so that the crystal orientation is in a metastable state. Form. After this metal film is heat-treated to stabilize its crystal orientation, it is patterned to form wiring.

[0013]

[Operation] According to the first method, grain growth is likely to occur (
111) A metal film is formed in a state where the density of oriented crystal grains is low, and this is heat-treated. At this time, adjacent (111)
Since grain growth progresses until oriented crystal grains come into contact with each other, a polycrystalline metal film with a large crystal grain size can be obtained. This makes it possible to obtain metal wiring that has excellent electromigration resistance and stress migration resistance.

[0014] The extreme state of low grain density is amorphous. When forming such an amorphous metal film, prior to heat treatment, a treatment to form a portion that will become a nucleus for grain growth,
For example, a process such as ion implantation of a certain type of metal may be added.

According to the second invention, a metal film is formed so that the crystal orientation becomes a metastable state, and the metal film is heat-treated to change the crystal orientation to a stable state. Residual stress within the film is reduced. Therefore, the stress migration resistance of the resulting metal wiring is improved.

[0016]

Embodiments Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a process diagram for manufacturing a semiconductor device according to an embodiment of the first method of the present invention.

As shown in FIG. 1(a), for example, a silicon substrate 1 is used as a semiconductor substrate, and a desired element including a diffusion layer 2 is formed according to a normal process. The substrate on which the elements are formed is covered with an insulating film 3 such as a CVD silicon oxide film, and necessary contact holes are formed therein. A titanium nitride (TiN) film 4 is then formed as a base film for metal wiring on the substrate on which the insulating film 3 is formed. At this time,
The TiN film 4 is deposited by a reactive bias sputtering method with controlled bias voltage, and is made into a (100) oriented crystal film, for example. TiN film 4 with such orientation control
After forming an Al film 5, an Al film 5 is formed thereon by sputtering.
form. Note that the Al film 5 may be an alloy film containing Si or the like. The same applies to the following examples.

The crystal orientation of the Al film is such that, for example, on an insulating film such as a silicon oxide film, the surface energy is minimized (
111) is usually preferred, but it is known that the crystal orientation changes depending on the underlying material, surface condition, and Al film deposition method. In this example, the base layer (10
As a result of forming the TiN film 4 with a 0) orientation, the density of crystal grains 6 with a (111) orientation in the Al film 5 obtained is very low, for example, 10 6 /cm 2 due to the influence of this base.

After forming an Al film with a low density of (111) oriented crystal grains in this manner, it was heated to 450°C.
The (111) oriented crystal grains 6 are grown until adjacent ones come into contact with each other by heat treatment in a forming gas of about An Al film 7 is used.

Thereafter, the Al film 7 is patterned according to a normal process to form wiring as shown in FIG. 1(c).

According to this embodiment, since the Al wiring is polycrystalline with large crystal grains, a wiring having high resistance to electromigration and stress migration can be obtained.

Note that the method for forming the (100) oriented TiN film is not limited to the reactive bias sputtering method. For example, by adjusting the temperature and gas flow rate using a pyrolysis method using a gas such as titanium tetrachloride and ammonia,
00) oriented TiN film can be obtained.

FIG. 2 shows the manufacturing process of another embodiment. The steps from forming an insulating film 3 on a substrate 1 on which elements are formed and forming contact holes thereto are the same as in the previous embodiment. Thereafter, in this embodiment, an Al film 10 is formed by sputtering while the substrate is being cooled. The state is shown in Figure 2(a).
It is. At this time, since the substrate is cooled, crystal grain growth in the Al film 10 is suppressed, and the Al film 10 becomes amorphous.

Next, this amorphous Al film 10 is coated with the film shown in FIG. 2(b).
), for example, by implanting Al ions at an appropriate concentration and linear density and performing heat treatment, crystal growth nuclei 11 are formed inside at a density of, for example, 10 6 /cm 2 .

Then, as in the previous example, heat treatment was performed in a forming gas to grow crystal grains, resulting in the crystal grains shown in FIG. 2(c).
As shown in the figure, polycrystalline Al with large grain size and (111) orientation
A membrane 12 is obtained. This polycrystalline Al film 12 is patterned to form wiring as shown in FIG. 2(d).

This embodiment also provides the same effects as the previous embodiment.

[0028] The embodiments so far have intentionally (111)
An Al film with a low density of oriented crystal grains was formed, and the crystal grains were grown to form a polycrystalline Al film with a large grain size. Next, an example of a second method will be described in which the Al film is formed with its crystal orientation set in a metastable state, and then changed to a stable state to alleviate stress.

FIG. 3 is a manufacturing process diagram of such an embodiment. The substrate 1 on which the elements were formed was covered with an insulating film 3 such as a silicon oxide film, contact holes were formed in this, and crystals were grown using the substrate exposed in the contact holes as seeds by solid-phase epitaxial growth (100 nm). ) oriented silicon film 21 is formed.

Next, on this silicon film 21, a film shown in FIG.
), an Al film 22 is formed using the ion cluster beam method. At this time, the Al film 22 reflects the crystal orientation of the underlying silicon film 21 and becomes a (110) oriented film in a metastable state. That is, <1 of the Al film 22
11> direction, the substrate is tilted from the substrate surface as shown in FIG. 3(b).

By subsequently performing heat treatment, the Al film 22 becomes an Al film 23 having a thermodynamically stable (111) orientation with lower surface energy than (110), as shown in FIG. 3(c). .

Then, the Al film 23 and silicon film 21 are patterned to form a pattern as shown in FIG. 3(d).
Form desired wiring.

According to this embodiment, the change in crystal orientation caused by the heat treatment after the Al film is formed acts in the direction of relieving the residual stress within the Al film. This is because as the crystal orientation changes and the Al atoms rearrange, the vacancies within the film are swept out to the outside, and the residual stress fixed by these vacancies can be released. therefore,
Not only hillocks and voids are reduced, but also wiring with excellent resistance to stress migration can be obtained.

After actually changing the orientation of the Al film from (110) to (111) using the method described above, the number of hillocks in the field of view was examined using an optical microscope, and it was found that only one hillock was present. On the other hand, in the conventional method of directly forming a (111) oriented Al film, the number of hillocks increased dramatically to 20.

Note that FIGS. 4(a) and 4(b) are characteristic diagrams showing the measurement results of X-ray diffraction intensity in this example. FIG. 4(a) is before heat treatment, and FIG. 4(b) is after heat treatment. Moreover, FIGS. 5(a) and 5(b) are characteristic diagrams showing the measurement results of X-ray diffraction intensity in the conventional method. Figure 5 (
Figure a) is before heat treatment, and figure (b) is after heat treatment.

FIG. 6 is a manufacturing process diagram of yet another embodiment. In this example, an Al film having a metastable crystal orientation is formed using ion beam sputtering. First, as shown in FIG. 6(a), a substrate 1 on which elements have been formed in the same manner as in the previous embodiments is covered with an insulating film 3, and a contact hole is formed in this. Next, as shown in FIG. 6(b), an Al film 22 having an orientation other than (111) is formed by ion beam sputtering.

The ion beam sputtering method is different from the normal plasma sputtering method in that it is possible to control the momentum of ions, and the quality of the film can be controlled using an assisted ion beam. For example, as schematically shown in FIG. 7, an ion beam 53 is applied to an Al target 51, and Al
Ions 54 are made to enter the substrate 52 with a predetermined momentum at an appropriate angle inclined from the normal direction of the substrate 52 as shown in the figure. At the same time, an assist ion beam 55 is made incident on the substrate 52 in the normal direction. By such a method, the Al film on the substrate is (1
11) It is possible to have an orientation other than 11).

Thereafter, heat treatment was performed in the same manner as in the previous example, and as shown in FIG. 6(c), (111)-oriented Al
A membrane 23 is obtained. This Al film 23 is patterned to form wiring as shown in FIG. 6(d).

In this manner, this embodiment also provides an Al wiring having excellent stress migration resistance.

[0040] In the above embodiments, the case where only Al wiring was used was explained, but in addition to Al film, (111)
The present invention can be similarly applied to the case of using other metals having a face-centered cubic lattice structure with minimum surface energy, such as Cu, Au, Ag, etc.

[0041]

As described above, according to the present invention, a semiconductor device having a polycrystalline metal interconnection with excellent migration resistance can be obtained by controlling the crystal grains and orientation of the metal interconnection.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a semiconductor device according to another embodiment.

FIG. 3 is a diagram showing a manufacturing process of a semiconductor layer according to still another example.

FIG. 4 is a characteristic diagram showing the measurement results of X-ray diffraction intensity in the method of the present invention.

FIG. 5 is a characteristic diagram showing the measurement results of X-ray diffraction intensity in a conventional method.

FIG. 6 is a diagram showing a manufacturing process of a semiconductor device according to still another embodiment.

FIG. 7 is a diagram showing an overview of ion beam sputtering.

[Explanation of symbols]

1...Silicon substrate, 2...diffusion layer, 3...Insulating film, 4...TiN film, 5...Al film, 6...(111) oriented crystal grains, 7...(111) oriented Al film, 10...Amorphous Al film, 11...Growth nucleus, 12...(111) oriented Al film, 21...(100) silicon film, 22...(110) oriented Al film, 23...(111) oriented Al film.

Claims (2)

[Claims] 1. A step of forming a desired element on a semiconductor substrate, a step of covering the surface of the substrate on which the element is formed with an insulating film, and opening a contact hole in the insulating film;
111) A step of forming a metal film in a state where the density of oriented crystal grains is low, a step of applying heat treatment to the metal film to grow crystal grains of the (111) orientation, and the metal film in which the crystal grains have grown. 1. A method for manufacturing a semiconductor device, comprising: forming a wiring by patterning the semiconductor device. 2. A step of forming a desired element on a semiconductor substrate; a step of covering the surface of the substrate on which the element is formed with an insulating film; forming a contact hole in the insulating film; and forming a crystal orientation on the insulating film. The method includes a step of forming a metal film controlled to be in a metastable state, a step of performing heat treatment to change the crystal orientation of the metal film to a stable state, and a step of patterning the metal film to form a wiring. A method for manufacturing a semiconductor device, characterized in that: