JPH0754139A - Sputtering target - Google Patents

Abstract

PURPOSE:To provide a sputering target excellent in the formability of an alloy film excellent in electric conductivity, workability, the formability of an oxidized film and other various properties. CONSTITUTION:This sputtering target is a composite target in which the area ratio of molybdenum and tantalum is requlated so as to regulate into, by atom, 15-50% molybdenum, and the balance tantalum with an incidental impurity. Thus, the target extremely small in specific resistance can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target suitable for producing an alloy film excellent in conductivity, workability, oxide film forming property and other properties.

[0002]

2. Description of the Related Art In recent years, attention has been paid to an active matrix type liquid crystal display device constituted by using a thin film transistor (TFT) using an amorphous silicon (a-Si) film as a switching element.

This is a large-area, high-definition, high-quality, and inexpensive panel display (using an amorphous glass substrate and an a-Si film that can be formed at a low temperature to form a TFT array. This is because there is a possibility that a flat television will be realized.

In order to make the display pixel of this active matrix type liquid crystal display device as small as possible and have a large area, it is necessary to make the signal line to the TFT, that is, the gate line and the data line thin and long.

For example, when the inverted stagger type TFT structure in which a gate electrode wiring is provided on the glass substrate side and an insulating film or an a-Si film is stacked on the glass substrate to form a TFT, the gate electrode wiring is thin and sufficient. It is required to be a material that has low resistance and can withstand various chemical treatments thereafter.

Heretofore, various metal films such as tantalum (Ta) and titanium (Ti) have been used as gate electrode wiring materials satisfying such requirements.

However, in recent years, in order to achieve a larger area and higher definition, a material having lower resistance, good workability, no film peeling, and excellent resistance to subsequent chemical treatments has been selected. Is desired.

When the stagger type TFT structure in which the drain and source electrode wirings are provided on the substrate side is used, the drain and source electrode wirings are required to have the above characteristics.

On the other hand, a semiconductor integrated circuit using a single crystal Si substrate has the same problem.

For example, an impurity-doped polycrystalline silicon film has been generally used for a gate electrode wiring of a MOS transistor used in a memory integrated circuit represented by a dynamic RAM. However, the resistivity of the polycrystalline silicon film is too high for further miniaturization and high integration of the device.

The resistivity is lower than that of the polycrystalline silicon film,
A material that can withstand high temperatures is molybdenum silicide (MoSi ₂ ) film.
When attempting to realize a dynamic RAM or the like having M bits or more, the resistance of the electrode wiring is still high.

[0012]

As described above, in the conventional semiconductor device using the a-Si film or the single crystal Si substrate, in order to further miniaturize the element and increase the degree of integration, the electrode is required. The problem is that the wiring resistance is high.

Further, as the electrode wiring, a stable electrode material having not only a small resistance but also excellent workability, excellent resistance to various chemical treatments, and good ohmic contact with Si is desired. .

The present invention has been made in view of the above points, and provides a sputtering target excellent in the formation of an alloy film excellent in conductivity, workability, oxide film forming property, and other various characteristics. It is intended for.

[0015]

The present invention provides a-S
As a result of systematically conducting an experimental study on various metals and alloy films as electric wiring materials for semiconductor devices using i films, polycrystalline silicon films, single crystal Si substrates, etc., tantalum (Ta) and molybdenum (Mo) are limited. Ta in the composition range
Alternatively, it has a much lower electric resistance than the electric resistance of the Mo film, and has a workability required as an electric wiring film,
It has been found that an electric wiring film for a semiconductor device, which is excellent in oxide film forming property, ohmic contact with silicon, and the like, can be obtained, and that a sputtering method is suitable for producing the electric wiring film for a semiconductor device. by.

That is, the present invention is a sputtering target which is a composite target in which the atomic ratio of molybdenum is 15 to 50%, the balance of tantalum and incidental impurities are adjusted by the area ratio of both.

Further, the reason for limiting the composition of the alloy film for electrode wiring obtained by the present invention will be explained. When the Ta content is less than 30 atomic percent in the composition of the alloy film produced by sputtering, the electrical resistance of the alloy film is reduced. Is large, the oxide film forming property and the mixed liquid cleaning property are poor, and the alloy film composition in which the Ta content exceeds 95 atomic percent has a good alloy film processability, oxide film forming property and mixed liquid cleaning property. However, since the electric resistance increases, the above range is set.

The composition of the formed alloy film is preferably such that Ta is 30 to 80 atomic percent, and more preferably the composition of the formed alloy film has Ta of 5 or less.
A composition of more than 0 atomic percent and 80 atomic percent or less is preferable. This is because film peeling can be effectively prevented by betting an amount in which Ta exceeds 50 atomic percent, that is, Mo is less than 50 atomic percent.

As the form of the sputtering target, a composite target obtained by combining both of the Mo member and the Ta member depending on the area ratio is preferable.

The reason for selecting the above target is as follows. As the composite target, the Ta plate and the Mo plate can be used as they are, so that the raw materials are easily available and a gas component having a smaller gas component than that of the sintered target is obtained. It can be mentioned.

In the sputtering target according to the present invention, it is desirable that the amount of carbon, nitrogen, hydrogen, oxygen and other impurity elements is small, but it is acceptable to include them in the range of 5 atomic percent.

[0022]

EXAMPLE A composite target was obtained by combining plate materials cut out from a commercially available Ta plate and a Mo plate having a purity of 99.9% and changing the area ratio of Ta and Mo.

Then, using the sputtering targets of various compositions thus prepared, in an argon atmosphere,
Sputtering was performed at room temperature to obtain alloy films having various film compositions shown in Table 1.

The obtained alloy film was subjected to various tests shown in Table 1 such as electric resistance, workability (dry etching) and oxide film forming property.

The results are shown in Table 1.

For comparison, various commercially available titanium (Ti), chromium (Cr), molybdenum (Mo), tantalum (Ta), and molybdenum silicide (MoSi ₂ ) sputtering targets having a purity of 99.9% are also described above. Various tests were conducted in the same manner as in.

The results are also shown in Table 1.

In Table 1, ◯ (good), Δ (somewhat good), and × (poor) were evaluated in terms of workability by CF ₄
The taper workability was determined by whether or not the taper angle can be controlled by the CF ₄ -based dry etching.

Regarding the thermal oxidative property, there is no pinhole at a temperature of about 400 ° C. and a withstand voltage of 3 × 10 ⁵ V / cm or more, 1
^{Depending on} whether or not an oxide film with a leak current of × 10 ^-10 A / mm ² or less can be obtained, there is no pinhole in forming the anodic oxide film, and a breakdown voltage of 3 × 10 ⁶ V / cm or more, 1 × 10 ^{− Ten}
It was carried out depending on whether or not an oxide film having a leak current of A / mm ² or less was obtained.

The ohmic contact with silicon was determined depending on whether or not the reaction occurred at a temperature of about 400.degree.

[0031]

[Table 1] As is clear from Table 1 above, the alloy film according to the present invention has a lower specific resistance than any of Ti, Cr, Ta, and MoSi ₂ after room temperature deposition. small. By performing a heat treatment after the deposition, an even smaller specific resistance is obtained.

Also, the workability by dry etching is M
It was as excellent as the oSi ₂ film and was easy to taper.

Although a good thermal oxide film is not formed with Mo, Ti, Cr or the like, a good thermal oxide film is obtained with the alloy film according to the present invention.

H ₂ SO ₄ used as a cleaning liquid
The resistance to the + H ₂ O ₂ mixture was also excellent.

Further, it has been confirmed that the ohmic contact with Si is excellent, the reaction with the SiO ₂ film is small, and the compatibility with the semiconductor device using Si is good.

As the electrode material of the semiconductor device, there are cases where thermal oxide film forming property, anodic oxide film forming property, strong acid treatment, etc. are required, and as shown in Table 1 in the conventional Mo electrode, these are favorably used. This cannot be done and the Ta electrode can perform these treatments, but there is a problem that the specific resistance is high.

In this respect, the Mo--Ta alloy film of the present invention has T
When the composition ratio of a is 30 atomic% or more, thermal oxide film forming property, anodic oxide film forming property, strong acid treatment, etc. can be favorably carried out, and moreover, the specific resistance is made significantly lower than that of Ta electrode,
When the Ta composition ratio is 95 atomic% or less, a specific resistance lower than that of the Mo electrode can be obtained.

In particular, as is clear from Table 1, when the composition ratio of Ta is 70% or less, Mo is obtained without heat treatment.
A specific resistance lower than that of the electrodes can be obtained.

[0039]

As described above, by using the sputtering target according to the present invention, it is possible to obtain an alloy film for electric wiring which has a very small specific resistance and is excellent in workability and stability. It is possible to achieve miniaturization and high integration of elements such as semiconductor devices, which is extremely useful industrially.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Takenori Umeki Inventor Takenori Umeki 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock Company Toshiba Yokohama Metal Works (72) Inventor Hosaku Koana 8 Shinsugita-cho, Isogo-ku, Yokohama-shi Kanagawa Toshiba Yokohama Metal Factory

Claims (1)

[Claims] 1. Molybdenum 15-50 in atomic percent
%, The balance of tantalum and incidental impurities, and the sputtering target which is a composite target adjusted by the area ratio of both.