JPH0864554A - Sputtering target material for forming thin film of thin film transistor - Google Patents

Abstract

PURPOSE: To provide a sputtering target material for forming the thin film of a thin film transistor, capable of forming a thin film which has a small number of particles and has little irregularity with time in a Ta concentration. CONSTITUTION: A sputtering target material has a composition which contains 1 to 20wt.% of Ta with the remnant of Al and irreversible impurities, and has a structure in which an intermetallic compound containing Al3 Ta of a mean particle diameter of 30μm or smaller as its main component, is dispersed in a base of a recrystallization texture of a mean crystal grain diameter of 30μm or smaller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target material for forming a thin film of a thin film transistor capable of forming a thin film having a small number of particles and a small Ta concentration variation over time.

[0002]

2. Description of the Related Art Conventionally, generally, for example, Japanese Patent Laid-Open No. 4-991.
No. 71, JP-A-6-25773, and JP-A-4-323871, when a thin film of a thin film transistor is formed by a sputtering method, Ta: 1 to 20 wt% is contained and the rest Is used a target material having a composition consisting of Al and unavoidable impurities, this target material, the Al alloy of the above composition is vacuum melted, cast into a water-cooled mold into an ingot, the ingot of a predetermined shape by cutting or the like. It is also known to be manufactured by processing into a plate material.

[0003]

On the other hand, the recent progress in sputtering technology has been remarkable, and along with this, there is a tendency for the film formation rate to be increased and the film formation area to be enlarged. Is used under the conditions of such high speed film formation and expanded film formation area, the conventional target material has substantially a cast structure, that is, Al
The particle size of the intermetallic compound mainly composed of ₃ Ta is 20 to 100.
variation over the range of μm, the crystal grain size of the base is also coarse,
Due to non-uniformity and the fact that pinholes and dendritic structures remain, particles are easily generated during film formation,
In addition, it is inevitable that the Ta concentration during film formation also varies with time.

[0004]

Therefore, the present inventors have
From the above viewpoint, as a result of focusing on the above conventional target material and conducting research to improve the quality,
When an Al alloy ingot having the same composition as that of the conventional target material is hot-rolled into a plate material having a predetermined shape and subjected to recrystallization heat treatment, the resulting plate material has a recrystallized structure of the base material. Not only can the crystal grains be sized to become fine grains with an average grain size of 30 μm or less, and the intermetallic compound can be finely sized by hot rolling to reduce the average grain size to 30 μm or less, Since the tissue (dendritic tissue) is destroyed and the pinhole disappears,
The research results have been obtained that when this is used as a sputtering target material, the number of particles in the thin film is significantly reduced and the variation in Ta concentration during film formation is also significantly small.

The present invention has been made based on the above-mentioned research results, and has a composition containing Ta: 1 to 20% by weight, the balance being Al and inevitable impurities, and an average particle size: 30 μm or less. An intermetallic compound mainly composed of Al ₃ Ta has a feature that it is a sputtering target material for forming a thin film of a thin film transistor, which has a structure in which a recrystallized structure having an average crystal grain size of 30 μm or less is dispersed in a base material.

In the sputtering target material of the present invention, the content of Ta is set to 1 to 20% by weight. When the content of Ta is less than 1% by weight, the stress migration resistance and the corrosion resistance brought about in the thin film by Ta are brought about. This is because the desired effect for improving the heat resistance cannot be obtained, and on the other hand, when the content exceeds 20% by weight, the electrical resistance of the thin film suddenly increases, and the intermetallic compound and the crystal grains of the base material are also increased. The average particle size of 30 μm or less is set to be 30 μm or less. When the average particle size exceeds 30 μm, the generation of particles and the variation in Ta concentration with time increase rapidly together with the coexistence of pinholes and dendritic structures. It is based on the reason.

[0007]

EXAMPLES Next, the sputtering target material of the present invention will be specifically described by way of examples. Vacuum degree 1 × 1
The molten Al alloy with the Ta content shown in Table 1 was melted in a vacuum melting furnace at 0 ^-4 torr or less and cast into an iron mold to form an ingot with a plane dimension of 200 mm x 200 mm and a thickness of 40 mm. The ingot is heated in air to a predetermined temperature within the range of 550 to 600 ° C., and then five passes of rolling are set as one cycle, and hot rolling is repeated three times to obtain a thickness of 8
mm rolled plate, and then this rolled plate was exposed to the air in Table 1
The recrystallization heat treatment of holding for 1 hour at the temperature shown in
Finally, each of the target materials 1 to 8 of the present invention was manufactured by cutting into a dimension of width: 300 mm × thickness: 5 mm × length: 600 mm. Also, for the purpose of comparison, similarly, an Al alloy molten metal having a Ta content shown in Table 1 was melted in a vacuum melting furnace having a vacuum degree of 1 × 10 ⁻⁴ torr or less, cast into a water-cooled copper mold, and a width: 315mm x thickness: 8mm x
A conventional target material 1 to 5 was manufactured by making an ingot having a length of 620 mm and finishing the same in the same dimension by cutting.

Then, with respect to the various target materials obtained as a result, the structures of the target materials at arbitrary 5 positions were observed, and the maximum and minimum grain sizes of the intermetallic compound and the crystal grains of the base were measured, Further, the average particle size was also obtained. The results are shown in Table 1. In addition, these various target materials were each made of pure In solder in the atmosphere at a temperature:
While being soldered to a backing plate made of oxygen-free copper at 180 ° C for 20 minutes, put it in a DC magnetron sputtering device and maintain a vacuum of 2 x 10 ^-4 torr while maintaining an Ar gas flow of 5 ml / min. Sputtering was performed at an output of 10 kW, and a thin film having a thickness of 1500 angstrom was formed 10 times on the surface of a glass substrate having a diameter of 100 mm. For each of the 10 thin films obtained as a result, the number of coarse particles having a diameter of 0.5 μm or more was measured using a particle counter, and the Ta content in the central part of the thin film was measured. The measurement results are shown in Table 2 as an average value, and the maximum and minimum values of Ta content are also shown.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

From the results shown in Tables 1 and 2, all of the target materials 1 to 8 of the present invention have a fine structure in which the crystal grains of the intermetallic compound and the base material have an average grain size of 30 μm or less,
Moreover, since there are almost no pinholes or dendritic structures, abnormal discharge does not occur during sputtering, and although the film formation area is large as described above, the number of particles is extremely small and Ta content is small. While it is possible to form a thin film whose variation with time is extremely small, in the conventional target materials 1 to 5, the crystal grains of the intermetallic compound and the base are relatively large grains, and the variation in grain size is large. Since it has a cast structure, pinholes and dendrites are present, which inevitably causes abnormal discharge during sputtering. Therefore, many particles are generated in the formed thin film, and Ta content is high. It is clear that the variation over time with respect to each other becomes relatively large. As described above, according to the sputtering target material of the present invention,
It is possible to form a thin film in which the generation of particles is extremely small and the variation in Ta content with time is extremely small, not to mention a wide film formation area, even in high-speed film formation.

Claims (1)

[Claims] 1. A composition containing 1: 1 to 20% by weight of Ta, the balance consisting of Al and inevitable impurities, and an average particle diameter: 3
The intermetallic compound mainly composed of Al ₃ Ta of 0 μm or less is
A sputtering target material for forming a thin film of a thin film transistor, which has a structure in which a recrystallized structure having an average crystal grain size of 30 μm or less is dispersed in a base material.