JP2003081694A - Ferroelectric thin film and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin ferroelectric films which is capable of controlling preferential crystal orientation even with relatively thick films of >=1 μm in film thickness with a simple process. SOLUTION: The thin ferroelectric films having uniaxial preferential orientability are manufactured by forming >=2 kinds of the thin ferroelectric films having a plurality of kinds of the preferential orientability on a polycrystalline Pt film formed on a substrate of any among a single crystal, polycrystals, or amorphous material by using an a chemical solution deposition process and an arc discharge reactive ion plating process. At this time, the substrate formed by disposing an SiO2 layer 102 on an Si substrate 101 and forming a Ti electrode layer 103 and a Pt electrode layer 104 thereon is used as a ground surface substrate and a ferroelectric seed layer 106 and a thin ferroelectric film layer 105 are successively formed on this substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric thin film capable of controlling particularly preferred crystal orientation and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, various film forming methods such as a sol-gel method, a vapor deposition method, a sputtering method and a CVD method have been reported as a method of forming a thin film of a ferroelectric compound represented by a perovskite type oxide. Particularly, in recent years, the arc discharge reactive ion plating method developed by the present inventor is an excellent method capable of forming a ferroelectric thin film at a high speed even at a relatively low film forming temperature.

In this method, as shown in FIG. 1, a source metal is heated and evaporated in a high-density oxygen plasma generated in a vacuum container 1 by a plasma gun 3, and each metal in the vacuum container 1 or a substrate 8 is evaporated. A ferroelectric oxide is formed by the reaction of steam and oxygen.

Usually, this type of film formation is carried out by using S with a thermal oxide film.
An i substrate (SiO ₂ / Si) on which a Pt / Ti lower electrode layer is sputter-deposited is used as a base substrate. Then, a ferroelectric thin film is formed thereon to obtain a sample having a thin film structure shown in FIG. The crystal structure of the ferroelectric thin film thus formed is Pt which is the base.
It largely depends on the crystal structure of the / Ti layer.

In FIG. 13, 101 is a Si substrate and 102 is S.
An io ₂ substrate, 103 is a Ti electrode layer, 104 is a Pt electrode layer, and 105 is a ferroelectric thin film layer.

[0006]

In the ferroelectric thin film as described above, the Pt layer is usually a polycrystalline thin film layer preferentially oriented in the (111) plane, and is grown on it. The ferroelectric thin film layer thus formed has no preferential orientation at all, or is the same as the Pt layer due to the devising of the film forming process (11
1) Only a thin film with preferential orientation is obtained.

For this reason, it is difficult to produce a (001) / (100) preferentially oriented film required for various types of ferroelectric / piezoelectric devices, and a case of producing a (111) preferentially oriented ferroelectric thin film. However, it is necessary to raise the substrate temperature at the time of film formation by 50 ° C. to 100 ° C. as compared with the normal process, or to reduce the film formation speed to half or less of that of the non-oriented film.

As described above, it is difficult to form a preferentially oriented ferroelectric thin film layer on a polycrystalline Pt layer,
It was a laborious task. Therefore, in order to obtain the above preferred orientation, various buffer layers (Y ₂ O ₃ , MgO, etc.) capable of heteroepitaxial growth on a Si substrate without a thermal oxide film are used.
It was necessary to grow TiN or the like first and then further heteroepitaxially grow the Pt layer thereon. This process requires a remarkably high temperature (650 ° C. or higher) as compared with the normal formation temperature of a polycrystalline Pt layer (up to 200 ° C.), and the growth rate of each layer is slower than that of a polycrystalline film (<1 μm / h).
r) Therefore, conventionally, the devices to which the heteroepitaxial process can be applied have been limited to the ferroelectric RAM (FRAM (registered trademark)) which is fine even if the film thickness of the thin film is 200 nm or less.

Further, it is extremely difficult to control the crystal orientation of a thin film for a device, such as a piezoelectric device, which cannot obtain a sufficient amount of displacement or generated force unless it has a film thickness of 1 μm or more. . In particular, it has been difficult to obtain a ferroelectric thin film having (001) or (100) preferential orientation different from the preferential orientation axis (111) of the polycrystalline Pt layer.

As a solution to this problem, a (001) or (100) -oriented seed layer is formed in advance as a base for forming a ferroelectric film, thereby forming (001) / (100).
Many methods for forming a preferential alignment film have been reported. The most famous example is lead zirconate titanate (PZT).
Is known as lead titanate (PT).

In this case, however, the permittivity and ferroelectric properties of PT, which is the seed layer, are lower than those of the desired ferroelectric substance, PZT, and the ferroelectric properties of the thin film as a whole are lower than those of PZT alone. There was a problem that it would end up. Further, in the case of a thick film having a thickness of 1 μm or more, the effect of the seed layer as the base becomes weaker as the thin film is deposited, and the preferential orientation tends to be lowered. Further, in piezoelectric applications, there is a problem that mechanical breakage easily occurs at the interface between the seed layer and the main thin film layer.

As described above, in the conventional method, in both the method using the hetero-epitaxial film and the method using the preferentially oriented seed layer, the crystal for the thick film of the ferroelectric oxide thin film exceeds 1 μm. Orientation control was extremely difficult.

The present invention has been made in view of the above problems, and provides a ferroelectric thin film capable of controlling the preferential crystal orientation even in a relatively thick film having a thickness of 1 μm or more, and a method of manufacturing the same. It is intended to be provided.

[0014]

The ferroelectric thin film and the method for manufacturing the same according to the present invention are configured as follows.

(1) In a ferroelectric thin film, a plurality of types of preferential crystal orientation ferroelectric oxide films were formed on a Pt film formed on a substrate.

(2) In (1) above, the substrate is made of any one of a single crystal, a polycrystal and an amorphous material, and a polycrystalline Pt film is formed on this substrate.

(3) In the above (1) or (2),
For the ferroelectric oxide film, a seed layer was formed on the Pt film by a chemical solution deposition method, and then a main thin film was formed by an arc discharge reactive ion plating method.

(4) In the above (3), the seed layer and the main thin film have the same composition.

(5) In the above (3) or (4),
At the calcination temperature in the range of 400 to 450 ° C., (100) is preferentially oriented, and in the calcination temperature in the range of 450 to 510 ° C. (11
1) was preferentially oriented.

(6) In the above (4), the ferroelectric is A
A ferroelectric compound represented by BO ₃ was used.

(7) In the above (6), the ferroelectric compound is lead-based ferroelectric oxide.

(8) In (7) above, the ferroelectric compound is a lead-based ferroelectric oxide of PT, PZT or PLZT.

(9) In any one of (1) to (8) above, the film thickness is formed to 1 μm or more.

(10) In the method of manufacturing a ferroelectric thin film, a Pt film is formed on a substrate, and a plurality of types of preferential crystal orientation ferroelectric oxide films are formed on the Pt film. I chose

(11) In the above (10), the single crystal,
A polycrystalline Pt film was formed on a substrate made of either a polycrystalline material or an amorphous material.

(12) In (10) or (11) above, a seed layer is formed on the Pt film by a chemical solution deposition method, and then a main thin film is formed by an arc discharge reactive ion plating method to form a ferroelectric substance. An oxide film was prepared.

(13) In the above (12), the seed layer and the main thin film have the same composition.

(14) In the above (12) or (13), (100) at a calcination temperature in the range of 400 to 450 ° C.
Preferred orientation, and (111) preferred orientation at a calcination temperature in the range of 450 to 510 ° C.

(15) In (13) above, the ferroelectric substance is a ferroelectric compound represented by ABO ₃ .

(16) In (15) above, the ferroelectric compound is a lead-based ferroelectric oxide.

(17) In (16) above, the ferroelectric compound is a lead-based ferroelectric oxide of PT, PZT, or PLZT.

(18) In any one of the above (10) to (17), the film thickness is formed to be 1 μm or more.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION A ferroelectric thin film and a method for manufacturing the same according to the present invention are a chemical solution deposition method (Cbemic
solution deposition (CSD method) and arc discharge reactive ion plating method, and is used on a polycrystalline Pt film formed on a single crystal, polycrystalline or amorphous substrate. A ferroelectric thin film having a uniaxial preferential orientation in which a plurality of types or more of ferroelectric oxide thin films having preferential crystal orientation are formed, and a method for producing the same.

In the above-mentioned chemical solution deposition method (CSD method), a precursor solution of a ferroelectric oxide is applied on a substrate and then rapidly heated in an oxygen atmosphere to remove the solvent and crystallize, and finally. It is widely known as a method of forming a ferroelectric thin film of about 100 nm.

The present inventor strictly controls the heat treatment temperature for rapid heating when forming the ferroelectric thin film on the Pt (111) electrode substrate by the CSD method.
It has already been reported that the crystal orientation of the thin film can be controlled preferentially ("PZT-based ferroelectric thin film forming method" Patent Publication No. 2995290 (registered October 29, 1999)). For example, in the case of a PZT (Zr / Ti = 53/47) thin film, a (100) preferred orientation is obtained by heat treatment at 450 ° C.
A film with (111) preferential orientation is obtained by heat treatment at 510 ° C. By using this method, the crystal orientation of the ferroelectric thin film can be controlled even on the polycrystalline Pt (111) preferential orientation film.

In the present invention, as shown in FIG.
A ferroelectric thin film preferentially oriented on the (100) or (111) plane is first formed by the SD method, the same film is used as a seed layer, and a ferroelectric thin film formed by an arc discharge reactive ion plating method is formed thereon. It is possible to control the preferential crystal orientation even in a relatively thick film (hereinafter referred to as a “thick film”) having a film thickness of 1 μm or more by performing the high-speed film formation.

Moreover, since the seed layer and the thick film can be made to have the same composition, the relative permittivity and the ferroelectric characteristics of the entire thick film structure are not impaired. Rather, the presence of the seed layer densifies the structure of the thick film deposited by the ion plating method, and improves the dielectric characteristics and the ferroelectric characteristics (PE hysteresis) in combination with the control of the crystal orientation. Furthermore, because of the same composition, the interface between the seed layer and the thick film is almost seamlessly bonded at the atomic level, and the mechanical strength is also very excellent.

Further, in the present invention, it is not necessary to consistently perform seed layer formation and thick film formation. Even if a seed layer formed in the atmosphere is used, the surface of the seed layer is cleaned and activated by the high-density plasma generated by arc discharge, and the preferred orientation of the seed layer is maintained while performing the seamless thick film growth described above. It This is MBE, sputtering,
This is in sharp contrast to the need for strict atmosphere control when controlling the orientation by the CVD method.

As described above, according to the present invention, the crystal orientation of the ferroelectric thick film is determined by the simple process of forming the preferentially oriented seed layer by the CSD method and forming the thick film by the arc discharge reactive ion plating method. It can be controlled to two preferred orientations of (100) or (111).
As a result, the preferentially oriented ferroelectric thick film has excellent ferroelectricity and piezoelectricity as compared with the conventional randomly oriented thick film.

[0040]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing the construction of the above-mentioned reactive arc discharge ion plating apparatus used in the examples. In the figure, 1 is a vacuum container (vacuum tank), 2
Is a carrier gas introduced into the vacuum vessel 1, 3 is a pressure gradient type arc discharge plasma gun (UR gun), 4 is a plasma gun intermediate electrode, 5 is a plasma gun anode, 6 is a magnetic field source for plasma control, 7 Is an evaporation source, 8 is a substrate, 9 is a heater for heating a substrate, 10 is a gas introducing pipe for the reaction gas 11,
12 is a shutter.

FIG. 2 is a sectional view showing the structure of the ferroelectric thin film manufactured in the embodiment, 101 is a Si substrate, 1
02 is a SiO ₂ layer, 103 is a Ti electrode layer, and 104 is Pt.
An electrode layer, 105 is a ferroelectric thin film layer, and 106 is a ferroelectric seed layer.

FIG. 3 is a flow chart showing the seed layer forming process by the above-mentioned chemical solution deposition method. In the figure, S1 is a spin coating process step (3000 rpm, 40 s), and S2 is a dry process (Dryi).
ng) treatment step (RT or 120 ° C.), S3 is a thermal decomposition (Pyrolysis) treatment step (400-520).
℃, 3-5 min), S4 is a firing process (RTA 30 ℃ / s, 650-700 ℃, 1 mi
n), and these processing steps are repeated.

Example 1 A seed layer of a ferroelectric multi-component oxide was formed by the CSD process shown in FIG. As a substrate, Ti (50 nm) and Pt (200 nm) were sequentially deposited by DC magnetron sputtering on a Si substrate (thickness: 300 to 550 μm) with a thermal oxide film of 500 to 1000 nm (Pt / Ti).
/ SiO ₂ / Si) was used. Then, as a seed layer material, a ternary complex oxide ferroelectric PZT [Pb (Zr _x
Ti _1-x ) O ₃ ], a thin film (film thickness: 100 nm) was prepared.

In this embodiment, the film composition is X = 63 (Z
r / Ti = 53/47) was formed. After stirring and mixing a metal alkoxide solution of Pb, Zr, and Ti as a CSD raw material was applied onto the substrate by spin coating, it was calcined at 450 ° C. to remove the solvent in the film. Then, crystallization of PZT was promoted by rapid thermal annealing treatment at 700 ° C. for 10 minutes in an oxygen stream to finally obtain a PZT seed layer having a film thickness of 100 nm. When the crystal structure of the seed layer was analyzed by X-ray diffraction, (10
It was found that the 0) plane was a perovskite type PZT in which the preferential orientation was made.

FIG. 4 shows the (100) preferentially oriented PZT.
It is a figure which shows the X-ray-diffraction pattern of a seed layer (film thickness: 100 nm).

A PZT thick film having the same composition was formed on the above PZT seed layer by the arc discharge reactive ion plating apparatus shown in FIG. Metals of Pb, Zr, and Ti were used as the material of the evaporation source 7, and they were evaporated independently by resistance heating and electron beam heating. The evaporation amount of each metal raw material was measured by a crystal vibration type film thickness monitor, and feedback control was performed on the heating source so as to maintain a constant evaporation amount during film formation. 50 to 100 sccm of H as carrier gas 2 in the pressure gradient type arc discharge plasma gun 3
Arc discharge was generated by introducing e and applying a DC bias voltage. Discharge voltage is 100-120V,
The discharge current was controlled at 50-100A.

The high-density plasma (plasma density> 10 ¹² cm ^-3 ) generated by this arc discharge was introduced into the vacuum chamber 1 by the magnetic field of about 50 to 300 Gauss generated by the magnetic field generating source 6 for plasma control. In this state, 200 to 300 sc of oxygen as the reaction gas 11 is supplied from the gas introduction pipe 10.
By introducing cm, high-density oxygen plasma and oxygen active species were generated in the vacuum container 1.

A thin film was formed on the substrate 8 heated to about 500 to 550 ° C. by the heater 9 in the presence of the oxygen active species. As for the evaporation amounts of Pb, Zr, and Ti, the composition of the final thick film is the same as that of the seed layer (Zr / Ti = 53/4).
It adjusted so that it might become 7).

The film formation rate in forming the PZT thick film by the ion plating method is as high as 3 μm / hr or more,
The film thickness was about 2 μm. FIG. 5 (a) shows the result of X-ray diffraction of the thick film thus obtained. Perovskite type PZT preferentially oriented to the (100) plane like the seed layer
It was confirmed that As a comparison, the X-ray diffraction pattern of the PZT thick film directly formed on Pt without using the seed layer is shown in FIG. 5B, but no preferential orientation is observed and the orientation is random. I understood it.

As described above, by using the preferentially oriented seed layer, the PZT thick film (film thickness: 2 μm) formed thereon is formed.
It was confirmed that the crystal orientation of m) can be controlled. When the film structure of the interface between the seed layer and the PZT thick film was evaluated by cross-sectional FE-SEM observation, it was found that the interface between the two did not show a clear contrast and was almost seamlessly bonded as shown in FIG. Became.

Next, with respect to the capacitor cell in which the Pt upper electrode was formed on the obtained PZT film, the characteristics of the ferroelectric substance and the piezoelectric substance were measured to examine the effect of the seed layer. For comparison, a PZ film formed on Pt without the seed layer
The characteristics of the T thick film were also evaluated. First, the evaluation results of the ferroelectric characteristics will be described.

FIG. 7 shows P of the PZT capacitor cell (pressure film).
It is a figure which shows a -E hysteresis curve. A very well saturated PE hysteresis curve was observed with and without the seed layer. However, PZ formed on the seed layer
The T-thick film has larger saturation polarization and residual polarization. It is considered that this is because the direction of the spontaneous polarization domain is aligned more than that of the random alignment due to the formation of the (100) preferential alignment film.

FIG. 8 is a diagram showing a piezoelectric displacement curve of the capacitor cell, where (a) is (100) preferential orientation, and (b).
Is non-oriented. Again, a good butterfly displacement curve was observed regardless of the presence or absence of the seed layer, indicating that the obtained PZT thick film has high piezoelectric characteristics. Films were also formed on the seed layer for piezoelectric displacement (1
It can be seen that the (00) preferential alignment film is largely displaced. It is considered that this is also because the directions of the domains were aligned by the preferential orientation.

When the piezoelectric constant of the (100) preferred orientation film was calculated by a bending model, a lateral effect piezoelectric constant d ₃₁ = −110 pm / V was obtained. This value is almost equal to the constant of bulk ceramics PZT, P
The ZT thick film showed very good characteristics.

As described above, it was found that the PZT thick film having the (100) preferential orientation excellent in the ferroelectric property and the piezoelectric property can be produced by the method of this embodiment. That is, it was found that a uniaxial preferentially oriented ferroelectric thin film capable of controlling preferential crystal orientation can be manufactured even with a relatively thick film having a thickness of 1 μm or more.

Example 2 Using the same CSD raw material as in Example 1, the same process as in Example 1 was used to obtain PZT (zr
/ Ti = 53/47) Seed layer as substrate (Pt / Ti / S
formed on iO ₂ / Si). However, calcination for removing the CSD solvent was performed at 510 ° C. higher than the temperature of Example 1 (450 ° C.) to obtain a PZT seed layer having a film thickness of 100 nm preferentially oriented to the (111) plane.

FIG. 9 is a diagram showing an X-ray diffraction pattern of the PZT seed layer (film thickness: 100 nm) which is preferentially oriented.

Next, a PZT thick film having a thickness of about 2 μm was formed on the seed layer by the arc discharge ion plating method under the same conditions as in Example 1. The obtained PZ
The result of X-ray diffraction on the T thick film is shown in FIG. For comparison, a case where a film is directly formed on Pt without using a seed layer is shown in FIG. Same as seed layer (1
11) It was found that the perovskite type PZT was preferentially oriented. Similar to Example 1, (111) preferred orientation P
It was found from the result of FE-SEM observation that the ZT thick film was also joined to the seed layer almost seamlessly.

When the ferroelectric characteristics and the piezoelectric characteristics were evaluated in comparison with the randomly oriented sample, as shown in the PE hysteresis curve of FIG. 11 and the piezoelectric displacement curve of FIG. 12, both the ferroelectric characteristics and the piezoelectric characteristics were seeded. The (111) preferentially oriented PZT thick film formed on the layer showed superior characteristics. In particular, in the case of the (111) preferentially oriented film, the saturation polarization and the remanent polarization were significantly larger than those in the random orientation. This is considered to be a result of preferential orientation in the <111> direction which is the spontaneous polarization direction of the PZT thick film having the composition of Zr / Ti = 53/47.

When the piezoelectric constant was calculated using the same model as in Example 1, the lateral effect piezoelectric constant d ₃₁ = −75.
A value of pm / V was obtained. This value is smaller than the value of Example 1, and for the piezoelectric characteristics, PZ of the composition of this example is used.
For the T thick film, the result is that the (100) preferred orientation is more advantageous than the (111) preferred orientation. However, as described above, the residual polarization of the (111) preferentially oriented PZT thick film is extremely large, and it is considered that the application to a pyroelectric device utilizing the temperature change of the spontaneous polarization is effective.

Thus, also in the method of this embodiment,
As in the above-mentioned embodiment, a (111) preferentially oriented PZT thick film having excellent ferroelectric properties and piezoelectric properties can be produced. That is, the following effects can be obtained in the present invention.

Formation of preferentially oriented seed layer by CSD method,
The crystal orientation of the ferroelectric thick film can be controlled to two preferential orientations (100) or (111) by a simple process of forming a thick film by the subsequent arc discharge reactive ion plating method. As a result, the preferentially oriented ferroelectric thin film has excellent ferroelectricity and piezoelectricity as compared with the conventional randomly oriented thin film. Depending on the film composition,
Generally, the (100) preferred orientation film has excellent piezoelectric properties,
11) The preferential alignment film tends to have excellent ferroelectric properties and pyroelectric properties. In the present invention, even when forming a ferroelectric thin film having the same composition, it is possible to freely control the preferential crystal orientation between (100) and (111) according to the purpose of the device to which it is applied. is there.

Polycrystalline Pt preferentially oriented to the (111) plane
If there is a layer, it is possible to form a (100) and (111) preferentially oriented ferroelectric oxide thin film thereon. Unlike the conventional dry process (MBE, sputtering, CVD, etc.), an epitaxial substrate need not be specially prepared. Therefore, a wide range of materials such as a Si wafer with a thermal oxide film, glass, and various metals can be used as the base. As a result, the degree of freedom in device design is significantly higher than that of the conventional method.

In the conventional method, the influence of the underlayer is reduced as the film thickness increases, and the preferential crystal orientation can be maintained only in the thin film having a film thickness of 1 μm or less. In the present invention, the preferential orientation of the seed layer is maintained until the film formation by the ion plating method is completed, and the preferential crystal orientation can be controlled even with a relatively thick film (thick film) having a film thickness of 1 μm or more. is there. In the examples, the result of a thick film having a film thickness of 2 μm is shown, but a ferroelectric oxide thick film with preferential orientation can be produced even with a film thickness of 10 μm. Since the same thickness film has a preferentially oriented structure, poling treatment for aligning the polarization axes is not necessary, and the device manufacturing process can be simplified.

Since the seed layer and the thin film can have the same composition, the relative dielectric constant and the ferroelectric characteristics of the entire film structure are not impaired. Furthermore, because of the same composition, the interface between the seed layer and the thin film is almost seamlessly bonded at the atomic level, and the mechanical strength is also very excellent.

It is not necessary to consistently perform seed layer formation and thin film formation. Even if a seed layer formed in the atmosphere is used, the surface of the seed layer is cleaned and activated by the high-density plasma generated by arc discharge, and the preferred orientation of the seed layer is maintained while performing the above-described seamless thin film growth. . This is in sharp contrast to the need for strict atmosphere control during orientation control by MBE, sputtering, and CVD.

The product range in which the present invention can be used is a piezoelectric transformer or piezoelectric inpark, a micromirror or lens drive type optical switch, an optical shutter, an optical modulator, etc., and an inkjet printer head drive source. is there.

Various sensors such as a vibration gyro, an acceleration sensor, an infrared (heat) sensor, an optical sensor, an ultrasonic sensor, an ultrasonic motor, an ultrasonic actuator, an optical scanner, a waveguide type optical switch, an optical shutter, There are an optical modulator and a minute light source unit for writing photographic paper.

[0070]

As described above, according to the present invention,
The following effects can be obtained.

(1) With a simple process, it is possible to obtain a ferroelectric thin film capable of controlling the preferential crystal orientation even with a relatively thick film having a thickness of 1 μm or more. This preferentially oriented ferroelectric thin film has excellent ferroelectricity and piezoelectricity as compared with a conventional randomly oriented thin film, and also has excellent pyroelectric properties.

(2) If there is a preferentially oriented polycrystalline Pt layer on the (111) plane, a ferroelectric oxide thin film preferentially oriented on (100) and (111) can be formed thereon. is there. Unlike the conventional dry process (MBE, sputtering, CVD, etc.), an epitaxial substrate need not be specially prepared. Therefore, a wide range of materials such as a Si wafer with a thermal oxide film, glass, and various metals can be used as the base. As a result, the degree of freedom in device design is significantly higher than that of the conventional method.

(3) In the conventional method, the influence of the underlayer is reduced as the film thickness increases, and the preferential crystal orientation can be maintained only in the thin film having a film thickness of 1 μm or less. In the present invention, the preferential orientation of the seed layer is maintained until the film formation by the ion plating method is completed, and the preferential crystal orientation can be controlled even with a relatively thick film (thick film) having a film thickness of 1 μm or more. Therefore, a ferroelectric oxide thick film with preferential orientation can be produced even with a film thickness of 2 μm to a film thickness of 10 μm. Since the same thickness film has a preferentially oriented structure, poling treatment for aligning the polarization axes is not necessary, and the device manufacturing process can be simplified.

(4) Since the seed layer and the thin film can have the same composition, the relative dielectric constant and the ferroelectric characteristics of the entire film structure are not impaired. Furthermore, because of the same composition, the interface between the seed layer and the thin film is almost seamlessly bonded at the atomic level, and the mechanical strength is also very excellent.

(5) It is not necessary to consistently perform seed layer formation and thin film formation. Even if a seed layer formed in the atmosphere is used, the surface of the seed layer is cleaned and activated by the high-density plasma generated by arc discharge, and the preferred orientation of the seed layer is maintained while performing the above-described seamless thin film growth. .
This is in sharp contrast to the need for strict atmosphere control during orientation control by MBE, sputtering, and CVD.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a reactive arc discharge ion plating apparatus.

FIG. 2 is a sectional view showing the structure of a ferroelectric thin film according to the present invention.

FIG. 3 is a flow chart showing a seed layer formation process by a chemical solution deposition method.

FIG. 4 is a diagram showing an X-ray diffraction pattern of the PZT seed layer of Example 1.

5 is a diagram showing an X-ray diffraction pattern of the PZT thick film of Example 1. FIG.

FIG. 6 is a cross section FE of the PZT thick film formed on the seed layer.
-Figure showing SEM image

7 is a diagram showing a PE hysteresis curve of the PZT thick film of Example 1. FIG.

8 is a diagram showing a piezoelectric displacement curve of the PZT thick film of Example 1. FIG.

9 is a diagram showing an X-ray diffraction pattern of the PZT seed layer of Example 2. FIG.

FIG. 10 is a diagram showing an X-ray diffraction pattern of the PZT thick film of Example 2.

FIG. 11 is a diagram showing a PE hysteresis curve of the PZT thick film of Example 2.

FIG. 12 is a diagram showing a piezoelectric displacement curve of a PZT thick film of Example 2.

FIG. 13 is a sectional view showing the structure of a conventional ferroelectric thin film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 vacuum container 2 carrier gas 3 pressure gradient type arc discharge plasma gun 4 plasma gun intermediate electrode 5 plasma gun anode 6 plasma control magnetic field generation source 7 evaporation source 8 substrate 9 substrate heating heater 10 gas introduction pipe 11 reaction gas 12 shutter 101 Si substrate 102 SiO ₂ layer 103 Ti electrode layer 104 Pt electrode layer 105 ferroelectric thin film layer 106 ferroelectric seed layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/316 H01L 21/316 X 27/105 27/10 444C 41/08 41/08 D 41/18 41 / 18 101D 41/187 101Z (72) Inventor Yoshiaki Yasuda 2-9-13 Nakameguro, Meguro-ku, Tokyo Within Stanley Electric Co., Ltd. (72) Inventor Masahiro Akamatsu 2-9-13 Nakameguro, Meguro-ku, Tokyo No. Stanley Electric Co., Ltd. (72) Inventor Masanao Tani 2-9-13 Nakameguro, Meguro-ku, Tokyo F-Term inside Stanley Electric Co., Ltd. (reference) 4G077 AA03 BC41 DA15 EF01 HA06 SA04 SB05 4K029 AA06 BA43 BB02 BD01 CA03 DD06 EA01 FA07 5F058 BA11 BD05 BF18 BF46 BH01 5F083 FR01 JA15 JA38 JA39 PR22 PR23 PR33 PR34

Claims (18)

[Claims] 1. A uniaxial preferentially oriented ferroelectric thin film, wherein a plurality of types of preferentially crystalline oriented ferroelectric oxide films are formed on a Pt film formed on a substrate. . 2. The ferroelectric thin film according to claim 1, wherein the substrate is made of any one of a single crystal, a polycrystal and an amorphous material, and a polycrystalline Pt film is formed on the substrate. . 3. The ferroelectric oxide film is characterized in that a seed layer is formed on a Pt film by a chemical solution deposition method, and then a main thin film is formed by an arc discharge reactive ion plating method. The ferroelectric thin film according to claim 1 or 2. 4. The ferroelectric thin film according to claim 3, wherein the seed layer and the main thin film have the same composition. 5. The preferential orientation to (100) at a calcination temperature in the range of 400 to 450 ° C., and the preferential orientation to (111) at a calcination temperature in the range of 450 to 510 ° C. 3. The ferroelectric thin film described in 3 or 4. 6. The ferroelectric thin film according to claim 4, wherein the ferroelectric is a ferroelectric compound represented by ABO ₃ . 7. The ferroelectric thin film according to claim 6, wherein the ferroelectric compound is a lead-based ferroelectric oxide. 8. The ferroelectric compound is PT, PZT, PLZ.
8. The ferroelectric thin film according to claim 7, wherein the ferroelectric thin film is any one of the lead-based ferroelectric oxides of T. 9. The ferroelectric thin film according to claim 1, which has a film thickness of 1 μm or more. 10. A uniaxial preferential method characterized in that a Pt film is formed on a substrate, and a plurality of types of ferroelectric oxide films having preferential crystal orientation are formed on the Pt film. Method of manufacturing oriented ferroelectric thin film. 11. The ferroelectric thin film according to claim 10, wherein a polycrystalline Pt film is formed on a substrate made of any one of a single crystal, a polycrystal and an amorphous material. Production method. 12. A ferroelectric oxide film is produced by forming a seed layer on a Pt film by a chemical solution deposition method, and then forming a main thin film by an arc discharge reactive ion plating method. Claim 10 or 1 characterized
1. The method for producing a ferroelectric thin film described in 1. 13. The method for producing a ferroelectric thin film according to claim 12, wherein the seed layer and the main thin film have the same composition. 14. A preferential orientation to (100) at a calcination temperature in the range of 400 to 450 ° C., and a preferential orientation to (111) at a calcination temperature in the range of 450 to 510 ° C. The method for manufacturing a ferroelectric thin film according to claim 12 or 13. 15. The method of manufacturing a ferroelectric thin film according to claim 13, wherein the ferroelectric substance is a ferroelectric compound represented by ABO ₃ . 16. The method of manufacturing a ferroelectric thin film according to claim 15, wherein the ferroelectric compound is a lead-based ferroelectric oxide. 17. The ferroelectric compound is PT, PZT, PL
The method for producing a ferroelectric thin film according to claim 16, wherein the lead-based ferroelectric oxide of ZT is used. 18. The method for manufacturing a ferroelectric thin film according to claim 10, wherein the film thickness is formed to 1 μm or more.