JPH05340853A - Method for evaluating grain of aluminum - Google Patents

Abstract

PURPOSE:To accurately observe the grain of aluminum which does not contain silicon using a metal microscope. CONSTITUTION:A silicon film 3 is grown on an insulation film 2 and then an aluminum alloy film 4 or an aluminum film is grown on the silicon film 3 without containing silicon. The aluminum alloy film 4 or an aluminum film and the silicon film 3 under it are subjected to crystalline growth by annealing, thus forming a silicon/aluminum-containing film 5. After the silicon/aluminum- containing film 5 is etched by an etching liquid and then the boundary of the grain is made clear, the grain is observed by a metal microscope.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum grain evaluation method, and more particularly to a silicon-free aluminum grain evaluation method.

[0002]

2. Description of the Related Art Aluminum is widely used as a wiring material for semiconductor integrated circuit devices. The grain size of the aluminum can be observed by a scanning electron microscope.

On the other hand, although it is possible to observe the grain size of an aluminum film containing silicon with a metallurgical microscope, it becomes difficult to observe the grain size when silicon is not contained. Therefore, the procedure shown in FIG. 2 is used. Has been through.

2 (a) and 2 (b) are cross-sectional views showing an example of the conventional method, and FIGS. 2 (c) and 2 (d) are plan views thereof. The observing method will be described below with reference to these figures. To do. First, as shown in FIG. 2A, an aluminum film 23 containing no silicon is deposited on the SiO ₂ film 22 grown on the substrate 21 by a sputtering method, and a silicon film having a film thickness of about several nm is further deposited thereon. The film 24 is formed by the same method.

After that, as shown in FIG. 2 (b), the silicon substrate 21 is put in a heating furnace and annealed at a temperature of about 530 ° C., so that the aluminum film 23 and the silicon film 24 on it are formed.
Is grown to form a silicon / aluminum containing film 25.

Next, a grain etching solution is used to slightly remove the crystal at the grain boundary portion of the silicon / aluminum-containing film 25 to clarify the boundary (FIG. 2 (c)). The grain will be observed with a metallurgical microscope.

[0007]

However, according to such a method, as shown in FIG. 2 (d), the silicon film 24 may remain on the silicon / aluminum-containing film 25 after annealing. Therefore, there is a problem that it is not possible to observe the grain accurately.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an aluminum grain evaluation method capable of accurately observing aluminum grains by a metallurgical microscope.

[0009]

The above-mentioned problems are solved by the step of growing a silicon film 3 on an insulating film 2 as shown in FIG. 1, and by not containing silicon on the silicon film 3. A step of growing an aluminum alloy film 4 or an aluminum film, and a step of crystallizing the aluminum alloy film 4 or the aluminum film and the silicon film 3 thereunder by annealing to form a silicon / aluminum containing film 5. , The silicon. The aluminum-containing film 5 is etched with an etching solution to clarify the boundaries of the grains, and then the grains are observed by a metallurgical microscope.

[0010]

[Operation] According to the present invention, the silicon film 3 is formed under the aluminum alloy film 4 or the aluminum film, and the silicon / aluminum containing film 5 is formed by crystal growth of the silicon film 3 by annealing. Membrane 5
Are etched to clarify the boundaries of the grains.

According to such a method, a part of the silicon film 3 remaining without being involved in the crystal growth does not cover the silicon / aluminum-containing film 5, so that an accurate grain can be observed by a metallographic microscope. To be done.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are sectional views showing an embodiment of the present invention, and FIGS. 1 (c) and 1 (d) are plan views thereof.

First, as shown in FIG. 1 (a), a silicon substrate 1 having a thickness of several hundreds nm is formed on the surface of the silicon substrate 1 by a thermal oxidation method or the like.
The O ₂ film 2 is grown. Then, a silicon film 3 is deposited to a thickness of 6 nm on the SiO ₂ film 2 by a sputtering method, and an aluminum alloy film 4 is further grown thereon to a thickness of 1 μm. The aluminum alloy film 4 is, for example, 0.1 wt% Cu (copper), 0.1
5 wt% Ti (titanium) is mixed with aluminum.

Thereafter, the silicon substrate 1 is put in a heating furnace (not shown) and annealed at a temperature of 525 ° C. for 30 minutes,
Crystals are grown by the reaction between the silicon film 3 and the aluminum alloy film 4 to form a silicon / aluminum containing film 5 (FIG. 1 (b)).

After that, the silicon / aluminum-containing film 5 is etched by using a grain etching solution prepared by mixing hydrofluoric acid, nitric acid, hydrochloric acid and water in the proportions of 1, 4, 4 and 20, respectively. From Figure 1 (c) to Figure 1
The state moves to the state shown in (d) and the boundaries of the grains are removed, and the outline becomes clear.

Next, the surface of the silicon-aluminum-containing film 5 containing silicon is observed by a metallographic microscope,
Thereby, the grain size of the aluminum alloy film 5 is measured.

According to such a method, the silicon film 3 does not cover the silicon / aluminum-containing film 5 even if a part of the silicon film 3 remains without participating in crystal growth. It enables accurate observation with a metallurgical microscope.

If a plurality of grain size data of good film quality are measured in advance and standardized, it becomes easy to evaluate the quality of the film by observing the grain size.

By the way, in the above-mentioned embodiment, the case of observing the grains of the aluminum alloy film 4 has been described. Conditions may be selected.

In the above embodiment, the observation of the grain size of the aluminum alloy film 4 has been described.
The same can be applied when observing the grain size of pure aluminum. That is, when a high-purity aluminum film is grown on a silicon film and these are annealed for crystal growth, observation with a metallurgical microscope becomes easy.

[0021]

As described above, according to the present invention, a silicon film is formed under an aluminum alloy film or an aluminum film, and the silicon film is crystal-grown by annealing to form a silicon film.
Since the aluminum-containing film is formed and the silicon-aluminum-containing film is further etched to clarify the boundaries of the grains, the silicon film remaining without being involved in crystal growth is formed by such a method. Since a part of the film does not cover the silicon / aluminum-containing film, it is possible to observe an accurate grain with a metallurgical microscope.

[Brief description of drawings]

FIG. 1 is a sectional view and a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view and a plan view showing an example of a conventional method.

[Explanation of symbols]

1 Silicon substrate 2 SiO ₂ film (insulating film) 3 Silicon film 4 Aluminum alloy film 5 Silicon / aluminum containing film

Claims (1)

[Claims] 1. A step of growing a silicon film (3) on an insulating film (2), and an aluminum alloy film (4) or an aluminum film containing no silicon on the silicon film (3). A step of growing, a step of crystallizing the aluminum alloy film (4) or the aluminum film and the silicon film (3) thereunder by crystal growth to form a silicon-aluminum containing film (5), An aluminum grain evaluation method characterized by observing the grain boundaries by etching the aluminum-containing film (5) with an etching solution to clarify the boundaries of the grains.