JP2507963B2 - Method of manufacturing oxide thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide thin film by an ion beam sputtering method.

[0002]

2. Description of the Related Art In the ion beam sputtering method, a target is irradiated with an ion beam from an ion source such as an ion gun.
This is a method in which a target constituent substance is knocked out by ion bombardment to form a film on a substrate. Compared to other sputtering methods such as DC sputtering and RF sputtering, the deposition atmosphere is 10
-The film can be formed at a low pressure of about ⁴ Torr and the substrate is not exposed to plasma, so that a high-quality film with less impurities mixed can be formed.

In a sputtering method including ion beam sputtering, generally, when a target peripheral object such as a part of the target plate is exposed on the surface of the target and is exposed to ions, the peripheral object such as the target plate is sputtered and generated. There is a problem that it is mixed as an impurity in the film.

As a means for preventing this, a method of covering a portion exposed to ions such as an exposed portion of the target dish with a cover is used. As the material of the cover, at least one kind of target material composed of one kind or two or more kinds of elements is used. Alternatively, a material having a low sputter rate and a high melting point other than the target material is used (JP-A-62-02).
No. 0866).

Further, in the ion beam sputtering method, there has been a method of preventing the sputtering of the target plate or the cover by making the diameter of the target sufficiently larger than the irradiation diameter of the ion beam.

[0006]

The problems of the above method are listed below.

When a film is formed by using the constituent material of the target material for the cover, the composition of the resulting film deviates from the composition of the target material because the cover is sputtered. It is very difficult to shift the composition of the target in consideration of the sputter rate of the cover and control the composition of the generated film. When a film is formed by using a material with a low sputtering rate and a high melting point for the cover, impurities are mixed in the formed film, although the amount is small compared with the case where the film is formed without the cover. JP-A-62-02086 mentioned above
6 According to JP-paste the molybdenum low sputtering rate, high melting point metal in a portion exposed to the plasma outside the target, target was a thin film using a SiO _2, can have a thin film of SiO ₂ Purity is 98.3%
Therefore, 1.7% of molybdenum was mixed as an impurity.

In the thin films for microdevices, new-function / high-function devices that are currently demanded, the above-mentioned compositional deviation and mixing of impurities pose practical problems.

The cost of film formation increases with the method of forming a film using a target having a diameter sufficiently larger than the irradiation diameter of the ion beam. Since the target area is proportional to the square of the radius of the target, when the diameter of the target is doubled, the amount of the target material becomes four times. In addition, the large-diameter target is difficult to handle because of its size and weight.

[0010]

The present invention is a method for producing an oxide thin film, which solves these problems when producing an oxide thin film by the ion beam sputtering method. The point is to cover the exposed portion of the target dish other than the target material with the ion beam with a graphite cover and irradiate the target with the ion beam in an oxygen-containing atmosphere to form an oxide thin film. It is a film. The important points of this oxide thin film production method are that the material of the cover is graphite (carbon) and that the film forming atmosphere contains oxygen.

[0011] Graphite has a low sputter rate, and in addition, in an atmosphere containing oxygen, sputtered carbon reacts with oxygen and changes into carbon dioxide. The carbon dioxide generated by the chemical change is exhausted to the outside of the film forming chamber by the exhaust system. Therefore, almost no impurities are mixed into the film due to the sputtering of the cover.

It is desirable that the graphite used for the cover has a high density such as pyrolytic graphite and highly oriented pyrolytic graphite. A sufficiently dense graphite cover has a small surface area and a small amount of adsorbed gas, so there is no problem with evacuation.

[0013]

Embodiments of the present invention will be described below. FIG. 1 shows a target plate used in the examples. The plate 2-1 is made of copper in order to quickly cool the target. The inside 2-2 of the dish is filled with an oxide powder as a target material and pressed at a pressure of 3 t / cm ² . Next, as shown in FIG. 1B, a cover 2-3 made of pyrolytic graphite is provided on the peripheral portion of the target plate where the copper is exposed. The above is the method for manufacturing the target.

FIG. 2 shows a sectional view of the film forming chamber 1 of this embodiment. The target 2 is installed at an angle of 15 ° from the horizontal, and cooling water is flowing through the target support base 3 to cool the target. The ion gun 4 is installed so that the ion beam enters the target at an angle of 45 °. The neutralizer 5 irradiates an electron beam to prevent the target surface from being charged up by an ion beam, and is installed so that the electron beam is horizontally incident. The substrate 6 is held vertically above the target with a tilt of 15 °, and a substrate heating heater 7 is arranged on the back surface of the substrate. A shutter 8 is arranged below the substrate, and a pipe 9 for introducing oxygen gas is arranged below the shutter 8 and inside the ion gun.

[0015] First of all, the film-forming chamber 1 10 ^{- 7} To
After evacuation to a high vacuum of rr or less, the ion guns 4 to 1.
2 × 10 ^- by introducing a ⁴ Torr argon gas, to start the discharge of the internal ion gun. After heating the substrate 6, oxygen gas is introduced to generate an ion beam and the target 2
Irradiation. After a few minutes of pre-sputtering, shutter 8
Is opened and a film is formed on the substrate 6.

The target 2 has a diameter of 13 cm and the ion beam has a diameter of 3 cm. However, due to the fact that the ion beam is incident on the target 2 at an angle of 45 ° and the spread of the ion beam, the target cover 1- Three
Is also exposed to the ions and sputtered. The sputtered carbon changes to carbon dioxide and is exhausted by the exhaust system.

[0017] to the target _{(Ba 0. 5, Sr 0} . 5)
FIG. 3 shows the dielectric constants of the thin films when TiO ₃ was used to form a film on a target cover using Ti, which is one of the constituent elements of the target, and when a film was formed using a pyrolytic graphite cover. With similar film thickness,
The thin film formed with the cover made of pyrolytic graphite has a higher dielectric constant than that using the cover made of Ti. The film having a thickness of 100 nm has a dielectric constant of 350 using the Ti cover, whereas the dielectric constant of the film using the pyrolytic graphite cover is improved by 420 and 20%. The composition analysis results are
Which was formed using a Ti-made cover Ba _{0. 4 8} Sr
_{0. 5 2 Ti 1. 1} 2 O is ₃ whereas, those using pyrolytic graphite cover Ba
_{0. 4 5} Sr _0. Close to _{5 0 Ti 1. 0 0 O} 3 and chemical composition. Further, carbon in the film was at an undetectable level.

[0018]

As described above, the oxide thin film produced according to the present invention has no impurities mixed therein and has a composition close to that of the target. As a result, the electrical properties of the thin film are significantly improved over conventional methods. Moreover, since it is not necessary to use a large-diameter target, the film formation cost can be suppressed and the target can be easily replaced.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a target used in an example according to the present invention.

FIG. 2 is a sectional view showing a configuration of a film forming apparatus used in the present invention.

FIG. 3 is a diagram showing experimental data of Examples.

[Explanation of symbols]

 1 Deposition Chamber 2 Target 2-1 Target Dish 2-2 Target Material 2-3 Cover 3 Target Support 4 Ion Gun 5 Neutralizer 6 Substrate 7 Heater 8 Shutter 9 Oxygen Gas Introduction Pipe

Claims (1)

(57) [Claims] 1. A method for producing an oxide thin film by an ion beam sputtering method, wherein a graphite cover is provided on a portion of a target plate where a material is exposed, and the film is formed in an oxygen atmosphere. Method for manufacturing thin film.