JP3446765B2 - Method and apparatus for producing oxide thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for producing a compound thin film such as an oxide by using reactive sputtering and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, a reactive sputtering apparatus used for forming an oxide crystal thin film has a structure as shown in FIG. 41 is evacuated to a vacuum from the exhaust port 42 in the vacuum chamber. An electric field is introduced from the direct current or high frequency power source 43 into the electrode / raw material target holder 44, and the electric field is applied between the substrate holder / electrode 45 capable of heating the substrate to generate plasma. Reference numeral 46 is a gas introduction port, and when forming an oxide thin film, for example, a sputtering gas such as Ar or an oxidation reactive gas such as O ₂ for oxidation is introduced. These gases are decomposed by plasma, ions in the plasma are accelerated and collide with the target 47, and an oxide thin film is deposited and formed on the substrate 48 by so-called sputter deposition. At this time, when the sputtered active particles reach the substrate, they undergo a catalytic reaction with reactive particles such as active oxygen ions and oxygen radicals in the plasma, resulting in oxidation that almost reflects the composition of the target constituent elements on the substrate. An object thin film is formed.

[0003]

However, in the method using such a conventional reactive sputtering apparatus, when the oxidation reaction is insufficient and a high quality oxide thin film is to be obtained,
Since it was necessary to extremely reduce the deposition rate and keep the substrate temperature at a relatively high temperature, there are various restrictions such as difficulty in combination with a semiconductor device and formation of a device on a low melting point substrate. However, there is a problem in that there are many restrictions in device design and manufacturing processes, and there is a high demand for formation at lower temperatures.

However, in the conventional continuous deposition method, the sputtered particles and the ionic charged particles, which are directed toward the substrate, continue to receive the impact caused by the collision with the film forming surface, so that good crystal growth is achieved. The formation of lattices and lattices was hindered, and it was difficult to form a sufficient oxide particularly in ideal crystal growth or low temperature formation.

In order to solve the above-mentioned conventional problems, it is an object of the present invention to produce an oxide thin film having few defects even when a thin film is formed at a relatively low temperature and having particularly good film quality and compactness. And

[0006]

In order to achieve the above object, the method for producing an oxide thin film according to the present invention is such that when an oxide thin film is deposited by sputtering, an oxidation reaction is performed by using discharge plasma of a gas containing at least oxygen. And a gas atmosphere containing ozone (O ₃ ) for compensating the oxygen deficiency portion in the thin film formed in the first step with oxygen atoms , And discharge atmosphere
Characterized by alternately repeating the second step of performing the oxidation reaction without exposing the deposited film to the sputtered particles and without exposing the deposited film to the sputtered particles. .

In the above structure, a mixed gas of a gas involved in the oxidation reaction during the deposition in the first step and an inert gas not involved in the oxidation reaction but only in the sputtering is supplied, and the oxidation is performed in the second step. It is preferable to supply only the gas containing the reactive element.

Further, in the above structure, when the first step and the second step are alternately performed a plurality of times, in both steps, the gas involved in the oxidation reaction during deposition and the sputtering not involved in the oxidation reaction are involved. It is preferable to supply a mixed gas of an inert gas that is only involved in this.

Next, an apparatus for producing an oxide thin film according to the present invention is a physical vapor deposition apparatus using sputtering, wherein vapor deposition means for depositing a thin film with an oxidation reaction using discharge plasma of a gas containing at least oxygen. And a gas atmosphere containing ozone (O ₃ ) for compensating the oxygen deficiency portion in the deposited thin film with oxygen atoms ,
Without exposing the electric atmosphere, means for performing an oxidation reaction of the deposited film in a state where the state a and the deposition process is not exposed to the sputtered particles without little or do without at all, the means for alternately repeating an oxidation reaction with the deposited It is characterized by having.

[0010] In the above configuration, inlet for supply of ozone, or is installed in the target electrode and the same vessel for causing sputtering sedimentary or without breaking the least vacuum, sputtering the deposition film
Preferably it has a structure between can move the container or region and the container or area for ozone oxidation treatment to.

Further, in the above structure, the substrate holder for supporting the substrate is rotated in order to move between the container or region for performing sputtering and the container or region for performing mainly oxidation reaction on or near the deposition surface by ozone treatment. It is preferable to provide a means for doing so.

In the above structure, it is preferable to use ultraviolet light as a source of ozone. Further, in the above configuration, it is preferable to use silent discharge as the ozone generation source. In the structure of the method and apparatus for manufacturing an oxide thin film of the present invention described above, in the second step of performing the oxidation reaction, substantially no deposition is performed, or the deposition rate is higher than that in the first step. Is preferably extremely small.

[0013]

The operation of the present invention is as follows. First
After the deposition step by reactive sputtering, the ozone gas used for ozone oxidation is introduced on or near the surface of the substrate (deposition) when the substrate is not exposed to the sputtered particles, that is, the deposition process is not or hardly involved. Then, atomic oxygen having strong reactivity is supplied, and an oxidation reaction step of the deposited thin film is performed. As a function of this step, the ozone gas near the surface is decomposed, a large amount of active atomic oxygen is generated, and oxygen vacancies in the thin film formed in the deposition step are compensated by oxygen atoms. Further, in the case of an oxide thin film, it has the effect of oxygenating the oxygen-deficient portion in the formed film, and binding excess oxygen to the oxygen and removing it in the form of O ₂ . By alternately repeating these two steps, even if formed at a relatively low temperature, there are few defects as a result, and there is an effect that an oxide thin film having particularly good film quality and compactness can be realized.

Although the oxide thin film is mainly described here, it is also useful for a nitride thin film and a hydride thin film, for example, and the operation is exactly the same.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a process of first depositing a target used for thin film deposition by reactive sputtering on a substrate or a substrate surface to be deposited, and generating ozone (O ₃ ) having a strong oxidizing action and the substrate surface and its By introducing in the vicinity, the steps of promoting oxidation and crystal growth by active oxygen on the surface of the deposition electrode are alternately repeated,
It forms a high quality oxide thin film at a relatively low temperature.

A representative embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a reactive sputtering apparatus capable of performing a plasma oxidation process, which is shown as an embodiment used in the present invention. 11 is a vacuum chamber, and exhaust port 1
It is evacuated to vacuum from 2. An electric field is introduced from the direct current or high frequency power supply 13 into the electrode / raw material target holder 14, and the electric field is applied between the substrate holder / electrode 15 capable of heating the substrate to generate plasma. Reference numeral 16 is a first gas inlet, for example, a sputtering gas such as Ar or a reactive gas such as O ₂ for oxidizing when forming an oxide thin film. These gases are decomposed by plasma and the ions in the plasma are accelerated and collide with the target 17, and if the substrate 18 is on the target by so-called sputter deposition, deposition and formation are performed on the substrate. At this time, when the sputtered active particles reach the substrate, they undergo a catalytic reaction with reactive particles such as active oxygen ions and oxygen radicals in the plasma, resulting in oxidation that almost reflects the composition of the target constituent elements on the substrate. An object thin film is formed. Reference numeral 19 denotes an ozone inlet for supplying active oxygen to the substrate by ozone oxidation treatment, which supplies oxygen gas to an ozone generation source 20 and generates ozone by, for example, silent discharge. Substrate holder-15
Are supported by, for example, a shaft 21, and the substrate 18 can be made to face a target or a plasma processing electrode by rotating the shaft.
Reference numeral 22 denotes an ozone-generating oxygen gas inlet, which is introduced into the ozone generation source 20 as described above.

Further, in the apparatus used in this embodiment, the partition 23 is provided in the area where the target is installed and the area where the plasma processing electrode for plasma processing is installed, and there is no hindrance to the rotation of the substrate holder. The atmosphere is a mixed gas of Ar, which is a sputtering gas, and O ₂ , which is a reactive gas, in the deposition process, while the structure is such that an O ₃ gas atmosphere, which is a reactive gas, is almost used in the ozone treatment process. There is.

As described above, in the first film deposition step, the substrate is placed on the target 17 and deposited on the substrate 18 by so-called sputter deposition. At this time, when the sputtered particles reach the substrate, a part of the particles contact-react with reactive particles such as active oxygen ions and oxygen radicals in the plasma to form an oxide thin film on the substrate.

In the second step of removing the defects in the oxide film and the deposited film, for example, by rotating the substrate holder,
The substrate is moved to a region where sputtered particles do not reach from the target or has a very low deposition rate, and is placed in a region where the excited species / active species generated by the discharge electrode 17 for plasma processing can be effectively irradiated and the substrate surface and its Promotes the oxidation reaction in the vicinity . The second step of this are the only effective at a relatively shallow area from the surface of the deposited film on the relationship between the time of the first deposition step time and the plasma processing step performs the optimum conditions are present, In any case, by performing at least these steps alternately, a dense and high-quality thin film can be deposited and formed at a relatively low temperature without causing substrate damage.

In the present embodiment, the gas atmosphere in the deposition process and the plasma treatment process is distinguished by having a structure provided with a partition, but the effect is large or small, but in the case where there is no partition, Ar gas is used over all the processes. It may be continued to flow as a mixed gas of oxygen, or may be a step of alternately switching the gas from the mixed gas to only the oxygen gas or from only oxygen to the mixed gas in accordance with the rotation of the substrate.

In FIG. 2, the substrate temperature is kept constant at 550 ° C.
The sputtering RF power density in the first deposition step was 0.3 W / cm ² , and the silent discharge of oxygen gas was used as the ozone generation source in the second step.
The change in relative permittivity of the formed lead titanate (PbTiO ₃ ) thin film is shown when 0% becomes ozonized and introduced into the container as a mixed gas of oxygen gas and ozone and the rotation speed of the substrate holder is 3 rpm. . In this embodiment, the target has a diameter of 6 inches (about 15 cm), the time for passing over the target is about 5 seconds, and the time for passing through the ozone treatment area is about 10 seconds. Under these conditions, about 1.5 nm is deposited. After that, about 1 ozone treatment
The condition is such that it is performed for 0 seconds. A clear difference is observed between the case of ozone treatment and the case of no treatment (rotation is carried out), and a clear improvement in the relative dielectric constant is seen during ozone treatment, as compared with the case without ozone treatment.

In the range of the rotation speed of about 1 to 10 rpm, there is a clear difference between the time of ozone treatment and the time of no treatment (rotation is carried out), but almost no change due to the number of rotations is observed.

As is clear from FIG. 2, the deposition and the oxidation treatment in the ozone atmosphere are alternately performed, so that the dielectric characteristics of the oxide dielectric thin film are improved even when the oxide dielectric thin film is formed at a relatively low substrate temperature. Was clear.

[0024]

As described above, according to the present invention, the plasma processing electrode is built in a different container which can be moved in the container of the apparatus or while keeping the reduced pressure state, and the sputtering method or the reactive sputtering method for a certain period of time. By performing the thin film deposition process by the method and the process of introducing ozone to the surface of the thin film that does not substantially deposit for a certain period of time and promoting the oxidation and crystal growth several times alternately, a good oxide thin film on a low temperature substrate can be obtained. Can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a thin film forming apparatus according to an embodiment of the present invention.

FIG. 2 shows the relative permittivity of a lead titanate thin film formed with and without ozone treatment when the substrate temperature is changed and the rotation speed of the substrate holder is 3 rpm to show the effect of the present invention. FIG.

FIG. 3 is a schematic view of a conventional general reactive sputtering apparatus.

[Explanation of symbols]

11 vacuum chamber 12 exhaust port 13 DC or high frequency power supply 14 electrode and target holder 15 Electrode and substrate holder 16 First gas inlet 17 Target 18 substrates 19 Ozone inlet 20 Ozone source 21 Substrate holder support shaft 22 Oxygen gas inlet for ozone generation 23 partitions

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ken Kamata               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Kazuki Komaki               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Takashi Hirao               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd.                (56) References JP-A-63-76868 (JP, A)                 JP-A-4-154963 (JP, A)                 JP-A-63-317670 (JP, A)                 JP-A-1-183416 (JP, A)                 Japanese Patent Laid-Open No. 2-50952 (JP, A)

Claims (8)

(57) [Claims] 1. When depositing an oxide thin film by sputtering, a first step of depositing a thin film with an oxidation reaction using a discharge plasma of a gas containing at least oxygen, and the first step In a gas atmosphere containing ozone (O ₃ ) for compensating the oxygen deficiency portion in the thin film with oxygen atoms , and not exposed to a discharge atmosphere, the deposited film is not exposed to sputtered particles and is deposited. A method for producing an oxide thin film, which comprises alternately repeating a second step in which an oxidation reaction is carried out with or without almost no steps. 2. In the first step, a mixed gas of a gas involved in an oxidation reaction during deposition and an inert gas not involved in an oxidation reaction but only in sputtering is supplied, and in the second step, oxidation is performed. The method for producing an oxide thin film according to claim 1, wherein only a gas containing a reactive element is supplied. 3. When the first step and the second step are performed alternately, in both steps, a gas involved in the oxidation reaction during deposition and an inert gas involved in the oxidation reaction but not in the oxidation reaction are involved. The method for producing an oxide thin film according to claim 1, wherein a mixed gas of gases is supplied. 4. In a physical vapor deposition apparatus by sputtering, a vapor deposition means for depositing a thin film with an oxidation reaction using discharge plasma of a gas containing at least oxygen, and oxygen deficiency in the deposited thin film. gas atmosphere der containing ozone (O ₃₎ for performing compensation by partial oxygen atoms
And a means for performing an oxidation reaction in a state where the deposited film is not exposed to a discharge atmosphere and the deposited film is not exposed to sputtered particles, and there is little or no deposition process, and the deposition and the oxidation reaction are alternately performed. An apparatus for producing an oxide thin film, comprising: 5. A container or a region where an inlet for supplying ozone is installed in the same container as a target electrode for causing sputtering deposition, or at least the deposition film is sputtered without breaking the vacuum. The apparatus for producing an oxide thin film according to claim 4, which has a structure capable of moving between a container and an area for performing ozone oxidation treatment. 6. A means for rotating a substrate holder for supporting a substrate for moving between a container or a region for sputtering and a container or a region for mainly performing an oxidation reaction on or near a deposition surface by ozone treatment. An apparatus for producing an oxide thin film according to claim 4. 7. The thin film manufacturing apparatus according to claim 4, wherein ultraviolet light is used as an ozone generation source. 8. The thin film manufacturing apparatus according to claim 4, wherein a silent discharge is used as an ozone generation source.