JPH10291885A - Method for producing oxide ceramic thin film - Google Patents

Abstract

(57) [Abstract] [Problem] Oxygen deficiency occurs in a festival for forming an oxide ceramic film. Conventional methods of compensating for this include firing in an oxygen atmosphere and post-treatment of oxygen plasma after crystallization, but all have been incomplete and cannot sufficiently compensate for oxygen deficiency. SOLUTION: After forming an amorphous film on a substrate, the amorphous film is crystallized after ozone treatment. In addition, ultraviolet irradiation is performed in the air or the like, and ultraviolet treatment and ozone treatment are performed simultaneously.

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 ceramic thin film which is a main component of a thin film device utilizing physical properties derived from crystallinity (piezoelectricity, pyroelectricity, ferroelectricity, etc.). The obtained oxide ceramics thin film is widely applied to electronic devices.

[0002]

2. Description of the Related Art The physical properties of a ceramic thin film material and the device characteristics when it is incorporated as a component of an electronic device greatly depend on the stoichiometric ratio of the constituent elements of the ceramic thin film. Above all, oxide ceramics are liable to cause oxygen deficiency (insufficiency), and this is often the main cause of characteristic deterioration. Most of the oxygen vacancies are caused by high-temperature treatment in the crystallization step. As a means for preventing this, firing in an oxygen atmosphere or treatment under atmospheric pressure or oxygen plasma treatment after crystallization is conventionally performed.

[0003]

However, in the above-described firing in an oxygen atmosphere, the oxygen deficiency is completely compensated, and the theoretical stoichiometric ratio, which is equal to the chemical composition ratio of the target ceramic material, is as follows. I can't achieve it. Further, even if an attempt is made to compensate for oxygen deficiency by post-treatment after crystallization, there is a problem that the treatment is insufficient or the treatment itself damages the crystal. In any case, it is difficult to make the chemical composition ratio of the ceramic material match the theoretical stoichiometry, and especially in the case of oxide ceramics, oxygen deficiency could not be completely compensated. As a result of intensive studies, the present inventors have found a method for producing an oxide ceramic having a composition close to the theoretical stoichiometric ratio without oxygen deficiency by simple means.

[0004]

According to the present invention, there is provided a method for producing an oxide ceramic thin film, comprising the steps of (1) forming an amorphous precursor film on a substrate; It is characterized by comprising a step of exposing in an atmosphere and (3) a step of crystallizing the same. Further, the method for producing an oxide ceramic thin film of the present invention comprises the steps of (1) forming an amorphous precursor film on a substrate and (2) exposing the precursor film to an ozone atmosphere (ozone Processing step) and (3) a step of crystallizing the same, wherein the steps (1) to (3) are performed n times (n
Is an integer of 2 or more). In the method for producing an oxide ceramic thin film of the present invention, the formation of an amorphous precursor film on the substrate is achieved by applying a sol made of an organometallic compound on the substrate and drying the sol. It is characterized by the following. Further, the method for producing an oxide ceramic thin film of the present invention is characterized in that the ozone treatment is achieved by irradiating ultraviolet rays in the air or in an atmosphere containing oxygen.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, when an amorphous precursor film formed on a substrate is subjected to ozone treatment, oxygen atoms are chemically bonded in the film, and then crystallization is performed by firing or the like. In the process, these oxygens do not escape, so
Thus, an oxide ceramics film that almost matches the theoretical stoichiometric ratio can be obtained. In addition, in the case of a manufacturing method having a step of applying a solution containing a raw material onto a substrate (a plurality of times), such as a sol-gel method, the coatability of the surface before application is determined by the quality of the film formed and the ceramic after crystallization. The quality of the film will be affected. If the surface before coating is treated with ozone as in the present invention, the surface wettability is greatly improved and the surface is also cleaned. Therefore, particularly in the case of multilayer coating (multilayer film), it is very uniform and flat. A ceramic thin film can be obtained. Therefore, the characteristics are also excellent.

Having described the operation, the present invention will be described in more detail with reference to the following examples.

(Example 1) A silicon wafer (4 inches in diameter, 250 μm in thickness) was prepared by forming Pt with a thickness of 0.2 μm on a silicon wafer by sputtering, and this was used as a substrate to be used later.

Next, a sol solution 1 containing predetermined concentrations of lead acetate and titanium tetraisopropoxide was prepared.
The sol solution 1 is spin-coated on the previously prepared substrate,
After drying in an 80 ° C. oven for 10 minutes, degreasing was performed in a 400 ° C. oven for 30 minutes, whereby an amorphous film having a thickness of about 0.2 μm was obtained on the substrate. This was placed in an acrylic container of 1 cubic meter (1 m on each side), and then the ozone generated by corona discharge of the atmosphere was introduced into the acrylic container with a silicon tube.
Ozone treatment was performed for minutes. The substrate was taken out of the container and baked at 800 ° C. for 1 minute in an oxygen atmosphere by a rapid temperature rising lamp annealing apparatus (RTA) to perform crystallization. The crystallized film thus obtained was analyzed by X-ray diffraction. As a result, perovskite-type lead titanate (PbTiO3) was analyzed.
(Hereinafter referred to as PT) (Sample 1).

On the other hand, without performing the ozone treatment, ceramic thin films were formed on the substrate in the same manner as in the preparation of Sample 1 in all other steps (three sheets, Comparative Examples 1 to 3). As a result of X-ray diffraction analysis of all three sheets, perovskite-type lead titanate (Pb
TiO3) (hereinafter referred to as PT). Further, for Comparative Examples 2 and 3, post-treatment after crystallization was performed. In Comparative Example 2, a plasma treatment under atmospheric pressure was performed as post-treatment, and in Comparative Example 3, an oxygen plasma treatment in an oxygen atmosphere of 0.01 Torr was performed as a post-treatment for 10 minutes.

The chemical composition ratios of the sample 1 obtained as described above and Comparative Examples 1 to 3 were analyzed by EDX. Assuming that the chemical composition ratio of the bulk PT prepared as a standard sample is a theoretical value, the analysis result of each sample estimated from this value is shown in Table 1.
Shown in

[0011] Lead titanate (PbTiO3) is a so-called ABO3-type oxide. As is clear from its chemical formula, the compositional ratio (molar ratio) of Pb: Ti: O = 1: 1: 3 is a theoretical value. . From Table 1, the composition ratio of each constituent element of Sample 1 according to the present invention is almost equal to the theoretical value. However, it can be seen that Comparative Examples 1 to 3 of the conventional method are significantly lacking in oxygen. From the above, it was found that ozone treatment of an amorphous film was very effective in maintaining the stoichiometric ratio after crystallization.

In this embodiment, the results of a comparative experiment for a PT film were introduced as an example, but similar results were obtained for other oxide ceramic films.

[0013]

[Table 1]

Example 2 A silicon wafer (diameter: 4 inches, thickness: 250 μm) was prepared by forming Pt by a thickness of 0.2 μm by sputtering, and this was used as a substrate to be used later.

This substrate was set in an RF sputtering apparatus, and a sputtered film having a thickness of 0.2 μm was formed on the surface of the substrate with a PbTiO 3 oxide target in an Ar / O 2 mixed gas atmosphere. When the obtained film was examined by X-ray diffraction, no crystalline peak was observed and it was found that the film was an amorphous film. After placing the substrate obtained above in an acrylic container of 1 cubic meter (1 m on each side), the ozone generated by corona discharge of the atmosphere was introduced into the acrylic container with a silicon tube, and the mixture was placed for 1 minute. Ozone treatment was performed. The substrate is taken out of the container, and is heated at 800 ° C. in an oxygen atmosphere by a rapid temperature rising lamp annealing apparatus (RTA).
For 1 minute to perform crystallization. When the crystallized film obtained as described above was analyzed again by X-ray diffraction, it was found to be perovskite-type lead titanate (PbTiO3) (hereinafter referred to as PT) (Sample 1).

On the other hand, a ceramic thin film was formed on a substrate in the same manner as in the preparation of Sample 1 except that the ozone treatment was not performed (three sheets, Comparative Examples 1 to 3). As a result of X-ray diffraction analysis of all three sheets, perovskite-type lead titanate (Pb
TiO3) (hereinafter referred to as PT). Further, for Comparative Examples 2 and 3, post-treatment after crystallization was performed. In Comparative Example 2, a plasma treatment under atmospheric pressure was performed as post-treatment, and in Comparative Example 3, an oxygen plasma treatment in an oxygen atmosphere of 0.01 Torr was performed as a post-treatment for 10 minutes.

The chemical composition ratios of Sample 1 and Comparative Examples 1 to 3 obtained as described above were analyzed by EDX. Assuming that the chemical composition ratio of the bulk PT prepared as a standard sample is a theoretical value, the analysis result of each sample estimated from this value is shown in Table 1.
Shown in

Lead titanate (PbTiO3) is a so-called ABO3 type oxide. As is clear from its chemical formula, the composition ratio (molar ratio) of Pb: Ti: O = 1: 1: 3 is a theoretical value. . From Table 1, the composition ratio of each constituent element of Sample 1 according to the present invention is almost equal to the theoretical value. However, it can be seen that Comparative Examples 1 to 3 of the conventional method are significantly lacking in oxygen. From the above, it has been found that ozone treatment of an amorphous film formed by sputtering is very effective in maintaining the stoichiometric ratio after crystallization.

In this embodiment, the results of a comparative experiment for a PT film were introduced as an example, but similar results were obtained for other oxide ceramic films.

[0020]

[Table 2]

Example 3 A silicon wafer (diameter: 4 inches, thickness: 250 μm) was prepared by forming Pt to a thickness of 0.2 μm by sputtering and used as a substrate to be used later.

Next, a sol solution 1 containing a predetermined concentration of lead acetate and zirconium acetylacetonate was prepared.
The sol solution 1 is spin-coated on the previously prepared substrate,
After drying in an 80 ° C. oven for 10 minutes, degreasing was performed in a 400 ° C. oven for 30 minutes, whereby an amorphous film having a thickness of about 0.2 μm was obtained on the substrate. This was placed in an acrylic container of 1 cubic meter (1 m on each side), and then the ozone generated by corona discharge of the atmosphere was introduced into the acrylic container with a silicon tube.
Ozone treatment was performed for minutes. By repeating the above steps from the spin coating to the ozone treatment four more times, an amorphous film having a thickness of about 1 μm was finally obtained on the substrate. The substrate was taken out of the container and baked at 800 ° C. for 1 minute in an oxygen atmosphere by a rapid temperature rising lamp annealing apparatus (RTA) to perform crystallization. When the crystallized film obtained as described above was analyzed by X-ray diffraction, it was found to be perovskite-type lead zirconate (PbZrO3) (hereinafter referred to as PZ) (sample 1).

On the other hand, a ceramic thin film was formed on a substrate in the same manner as in the preparation of Sample 1 except that ozone treatment was not performed (three sheets, Comparative Examples 1 to 3). The results of the X-ray diffraction analysis of all three sheets showed that the perovskite lead zirconate (P
bZrO3) (hereinafter referred to as PZ). Further, for Comparative Examples 2 and 3, post-treatment after crystallization was performed.
Comparative Example 2 performed plasma treatment under atmospheric pressure as a post-treatment,
In Comparative Example 3, oxygen plasma treatment was performed for 10 minutes in an oxygen atmosphere of 0.01 Torr as a post-treatment.

The chemical composition ratios of Sample 1 and Comparative Examples 1 to 3 obtained as described above were analyzed by EDX. Assuming that the chemical composition ratio of the bulk PT prepared as a standard sample is a theoretical value, the analysis result of each sample estimated from this value is shown in Table 1.
Shown in

Lead zirconate (PbZrO3) is a so-called ABO3 type oxide, and as is clear from its chemical formula, the composition ratio (molar ratio) of Pb: Zr: O = 1: 1: 3.
Is the theoretical value. From Table 1, the composition ratio of each constituent element of Sample 1 according to the present invention is almost equal to the theoretical value. However, it can be seen that Comparative Examples 1 to 3 of the conventional method are significantly lacking in oxygen. From the above, it was found that ozone treatment of an amorphous film was very effective in maintaining the stoichiometric ratio after crystallization.

In this embodiment, the results of a comparative experiment for a PZ film were introduced as an example, but similar results were obtained for other oxide ceramic films.

[0027]

[Table 3]

Example 4 A silicon wafer (4 inches in diameter, 250 μm in thickness) having Pt formed thereon to a thickness of 0.2 μm on a silicon wafer was prepared and used as a substrate to be used later.

Next, a sol solution 1 containing predetermined concentrations of lead acetate and zirconium acetylacetonate was prepared.
The sol solution 1 is spin-coated on the previously prepared substrate,
After drying in an 80 ° C. oven for 10 minutes, degreasing was performed in a 400 ° C. oven for 30 minutes, whereby an amorphous film having a thickness of about 0.2 μm was obtained on the substrate. This was treated in an air atmosphere with a Xe ultraviolet lamp for 30 seconds. At this time,
This means that the amorphous film on the substrate was subjected to the ultraviolet treatment and the ozon treatment at the same time. From the above spin coating to X
e By repeating the process up to ultraviolet lamp treatment (simultaneously with ozone treatment) four more times, an amorphous film having a thickness of about 1 μm was finally obtained on the substrate. The substrate was taken out of the container and baked at 700 ° C. for 1 minute in an oxygen atmosphere using a rapid temperature rising lamp annealing apparatus (RTA) to crystallize. The crystallized film obtained as described above was analyzed by X-ray diffraction. As a result, perovskite-type lead zirconate (PbZ
rO3) (hereinafter referred to as PZ) (Sample 1).

On the other hand, instead of the Xe ultraviolet lamp, the ozone treatment used in Examples 1 to 3 was performed, and in all other steps, a ceramic thin film was formed on the substrate in the same manner as in the preparation of Sample 1 described above ( Comparative example 1). The obtained film was subjected to X-ray diffraction analysis. As a result, perovskite-type lead zirconate (PbZrO3) was obtained.
(Hereinafter referred to as PZ). However, in Comparative Example 1, the half width of the diffraction peak was wide and the crystallinity was somewhat inferior to that of Sample 1 (Table 4). this is,
This indicates that the ultraviolet treatment before crystallization is effective at a low crystallization temperature thereafter. This is reflected in the stoichiometric ratio. From Table 4, focusing on the Pb amount, Comparative Example 1 is slightly insufficient in Pb amount as compared with Sample 1. This is probably because Pb evaporated before being sufficiently incorporated into the crystal lattice during the crystallization process. Therefore, it has been found that the ozone treatment also serving as the ultraviolet treatment is very effective in maintaining the stoichiometric ratio of the oxide ceramic thin film finally obtained.

In this embodiment, the results of a comparative experiment for a PZ film were introduced as an example, but similar results were obtained for other oxide ceramic films.

[0032]

[Table 4]

[0033]

As described above, when an oxide ceramic film is formed, by performing ozone treatment before crystallization of the amorphous film, the stoichiometric ratio of the finally obtained ceramic film is theoretically reduced. It will be close to the value. If an ultraviolet treatment is used together with ozone, the effect may be even greater.
In particular, a large amount of oxygen was unavoidable with the conventional method for oxygen, but the present invention has solved this problem.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 41/187 H01L 41/18 101C 41/24 101B 41/22 A

Claims (4)

[Claims] 1. A step of forming an amorphous precursor film on a substrate, a step of exposing the precursor film to an ozone atmosphere, and a step of crystallizing the precursor film. A method for producing an oxide ceramic thin film, comprising: (2) a step of forming an amorphous precursor film on a substrate; (2) a step of exposing the precursor film to an ozone atmosphere (an ozone treatment step); A method for producing an oxide ceramic thin film, comprising: a step of crystallizing the oxide ceramic thin film, wherein the steps (1) to (3) are repeated n times (n is an integer of 2 or more). . 3. The formation of an amorphous precursor film on a substrate,
3. The method for producing an oxide ceramic thin film according to claim 1, wherein the method is achieved by applying and drying a sol made of an organic metal compound as a raw material on a substrate. 4. The oxide according to claim 1, wherein the amorphous precursor film on the substrate is subjected to ozone treatment by irradiating ultraviolet rays in the air or in an atmosphere containing oxygen. Manufacturing method of ceramic thin film.