TW201724265A - Oxide dielectric element and method for manufacturing oxide dielectric element - Google Patents

Abstract

The present invention provides a technique for a protective film for an oxide dielectric element so that it is possible to improve the piezoelectric properties by lowering the restraining force provided by the protective film, suppress a decrease in permittivity, and prevent a decrease in physical properties caused by deterioration in reduction due to hydrogen ions. This oxide dielectric element 15 is provided with a Si substrate 1 and an oxide dielectric thin-film laminate layer 8 that is provided on the Si substrate 1 and has first and second electrode layers 4, 6 provided on either side of an oxide dielectric layer 5. The oxide dielectric thin-film laminate layer 8 is covered with a protective film 7 comprising a polymer having a high molecular weight. The protective film 7 can be formed using vapor deposition polymerization.

Description

Oxide dielectric element and method of manufacturing oxide dielectric element

The present invention relates to a protective film for an oxide dielectric element, and more particularly to a technique for providing a protective film by a polymer.

A thin film made of lead zirconate titanate (Pb(Zr,Ti)O ₃ ) which is excellent in piezoelectricity and ferroelectricity, which is PZT, is used in non-volatile memory. Body (FeRAM) use. In addition, the film composed of bismuth-tellurium-titanium (BST) is more often used in the normal dielectric phase than the use of its strong dielectric property because of its low Curie point. The high dielectric constant is used for variable capacitor applications.

Furthermore, in recent years, with the integration of MEMS (Micro Electro Mechanical Systems) technology, MEMS piezoelectric elements have also become practical. For example, as a main device, an application example extended to an inkjet head (actuator) or an angular velocity sensor, a gyro sensor, or the like can be cited.

However, an oxide dielectric element using an oxide dielectric such as PZT, for example, is inferior in piezoelectric characteristics in order to prevent reduction of hydrogen gas. In the past, a protective film was completely provided on its surface.

Conventionally, as such a protective film material, cerium oxide (SiO ₂ ) has been used, and a method of producing it by a CVD method (chemical vapor deposition method) or a sputtering method has been used.

However, since the protective film composed of ruthenium oxide has a large modulus of elasticity, the piezoelectric properties or the dielectric constant of the piezoelectric body are lowered by the restraining force, and the reduction due to hydrogen ions at the time of film formation of the protective film is caused. A problem of degraded physical properties.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2013-149669

The present invention has been made to solve the above-described problems of the prior art, and an object of the invention is to provide a physical property which can improve the physical properties such as piezoelectric characteristics and dielectric constant while reducing the binding force due to a protective film, and prevent hydrogen ions from being caused by hydrogen ions. A technique for reducing a protective film of a deteriorated physical property of an oxide dielectric element.

In order to achieve the above object, the present invention provides an oxide dielectric device comprising: a substrate; and a substrate provided on the substrate An oxide dielectric thin film layered body of the first and second electrode layers provided with an oxide dielectric layer; and the protective dielectric film formed of the polymer dielectric thin film layered body The oxide dielectric component covered.

In the present invention, the protective film is also effective in the case of polyurea.

In the present invention, the protective film is also effective in the case of a composition of parylene or a derivative of parylene.

In the present invention, the oxide dielectric layer is also highly effective in the case of a lead zirconate titanate.

In the present invention, the above oxide dielectric layer is also effective in the case of yttrium-yttrium-titanium.

On the other hand, the present invention is a method for producing any of the above oxide dielectric devices, and preparing an oxide dielectric film laminate having the first and second electrode layers provided next to the oxide dielectric layer. The module provided on the substrate has a step of forming the protective film by a vapor deposition polymerization method.

According to the present invention described above, the elastic modulus of the protective film composed of the polymer polymer is extremely small compared to the cerium oxide of the ceramic, so that physical properties (for example, piezoelectric characteristics or dielectric constant) can be greatly improved.

Further, according to the present invention, in the vapor deposition polymerization, by-products, particularly hydrogen, are not generated, so that the physical properties of the oxide dielectric layer are not deteriorated due to reduction by hydrogen ions.

Further, the vapor deposition polymerization method used in the present invention, the raw material list The vapor of the body bypasses the periphery of the film formation object and undergoes polymerization reaction on the surface of the film formation object. Therefore, the oxide dielectric film laminate of the module having irregularities can be formed with excellent step coverage. The protective film can thereby improve the insulation of the protective film.

1‧‧‧矽 substrate (matrix)

2‧‧‧Oxide layer

3‧‧‧Underground

4‧‧‧1st electrode layer

5‧‧‧Oxide dielectric layer

6‧‧‧2nd electrode layer

7‧‧‧Protective film

8‧‧‧Oxide dielectric thin film laminate

10‧‧‧ modules

15‧‧‧Oxide dielectric components

Fig. 1 is a cross-sectional view showing a configuration example of an oxide dielectric element according to the present invention.

2(a) to (e) are drawings showing an example of a method for producing an oxide dielectric device of the present invention.

FIG. 3 is a view showing a schematic configuration example of a vapor deposition polymerization apparatus used in the first vapor deposition polymerization method.

Fig. 4 is a view for explaining an example of the procedure of the second vapor deposition polymerization method.

Fig. 5 is a view showing the evaluation results of the examples and comparative examples.

Hereinafter, the form for carrying out the invention will be described with reference to the drawings.

Fig. 1 is a cross-sectional view showing a configuration example of an oxide dielectric element according to the present invention.

As shown in FIG. 1, the oxide dielectric device 15 of the present embodiment includes, for example, a first substrate and a second electrode layer 4 provided on the ruthenium substrate (base) 1 with the oxide dielectric layer 5 interposed therebetween. , an oxide dielectric thin film laminate 8 of 6.

In the oxide dielectric thin film laminate 8 of the present example, a lower layer 3 made of yttrium oxide (SiO ₂ ) layer 2 and titanium (Ti) and platinum (Pt) are sequentially formed on the tantalum substrate 1 of the semiconductor substrate. The first electrode layer 4, for example, lead zirconate titanate (Pb(Zr, Ti)O ₃ ), that is, an oxide dielectric layer 5 made of PZT or yttrium-tellurium-titanium (BST), platinum ( Pt) The second electrode layer 6 is formed.

Further, the oxide dielectric film laminate 8 is covered with a protective film 7 made of a polymer polymer to be described later.

In the case of the present invention, the elastic modulus of the protective film 7 is preferably as small as possible from the viewpoint of reducing the piezoelectric properties of the oxide dielectric element 15 and improving the piezoelectric characteristics or suppressing the decrease in the dielectric constant. .

According to the related viewpoint, the elastic modulus of the preferred protective film 7 is 10 GPa or less.

Further, the oxide dielectric element 15 of the present embodiment has the first extraction electrode 13 that is electrically connected to the first electrode layer 4 through the metal material 11 provided in the first contact hole 7a of the protective film 7, and is filled with permeation. The metal material 12 in the second contact hole 7b and the second extraction electrode 14 electrically connected to the second electrode layer 6 are provided.

2(a) to (e) are drawings showing an example of a method for producing an oxide dielectric device of the present invention. Hereinafter, an example of a method for producing an oxide dielectric device according to the present invention will be described with reference to FIGS. 2(a) to 2(e), FIG. 3 and FIG.

In this example, first, as shown in FIG. 2(a), it is prepared to have, for example, a plurality of thin film layers (yttria layers) formed on the tantalum substrate 1. 2. The module 10 of the oxide dielectric thin film laminate 8 of the lower layer 3, the first electrode layer 4, the oxide dielectric layer 5, and the second electrode layer 6).

Next, as shown in FIG. 2(b), a protective film 7 made of a polymer is formed on the oxide dielectric film laminate 8, whereby the protective film 7 is entirely covered with an oxide dielectric. A thin film laminate 8.

In the case of the present invention, the method for forming the protective film 7 is not particularly limited, and the vapor deposition polymerization method described below can be suitably used.

In the present specification, the vapor deposition polymerization method refers to a method in which one or a plurality of low molecular weight raw material monomers are polymerized on the surface of a substrate to form a polymer film.

As such a vapor deposition polymerization method, a raw material monomer of a plurality of types of low molecular organic materials having a high vapor deposition reactivity is known, and a method of polymerizing these plural raw material monomers on a surface of a substrate to form a polymer film is known (hereinafter referred to as "First vapor deposition polymerization method"), and a dimer of a specific organic material is thermally decomposed to generate a radicalized raw material monomer, and the raw material monomer is polymerized on the surface of the substrate to form a polymer film. The method (hereinafter referred to as "second vapor deposition polymerization method") can be applied to any method in the present invention.

FIG. 3 is a view showing a schematic configuration example of a vapor deposition polymerization apparatus used in the first vapor deposition polymerization method.

As shown in Fig. 3, the vapor deposition polymerization apparatus 20 of the present embodiment has a vacuum chamber 22 connected to the vacuum evacuation unit 21, and the lower portion of the vacuum chamber 22 is loaded on the stage 24 having the temperature control means 23. The module 10 is placed as a film formation object.

Here, a pair of evaporation sources 25 and 26 for evaporating two kinds of raw material monomers are provided above the vacuum chamber 22, and the pair of evaporation sources 25 and 26 respectively intervene the introduction tubes having the valves 27a and 28a. 27, 28 are respectively connected to the upper portion of the vacuum chamber 22.

Further, a heater 29 for heating the vapor of the raw material to be introduced is provided in the upper portion of the vacuum chamber 22.

Each of the evaporation sources 25 and 26 of the vapor deposition polymerization apparatus 20 is provided with an evaporation container (not shown) so that the raw material monomers for forming the protective film 7 are separately injected into the respective evaporation containers. internal.

In the case of the present invention, the material for forming the protective film 7 by the first vapor deposition polymerization method is not particularly limited, and it is considered that the influence of high temperature on the device during the reaction is suppressed, and the prevention of hydrogen ions causes the oxide dielectric layer 5 to be formed. The reduction of the reduction is preferably carried out using a reaction temperature which is low, and it is preferred that no by-products, particularly hydrogen, are generated during the polymerization.

From a related point of view, the material of the protective film 7 is preferably polyurea.

When the polyurea film is formed by the first vapor deposition polymerization method, a diamine monomer and an acid component monomer can be used as a raw material monomer.

In the case of the present invention, as the diamine monomer, for example, 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl ether (DDE), or 4, 4 can be suitably used. An alicyclic or aliphatic group such as -methine bis (cyclohexylamine) (H12MDA) (4,4'-diaminodicyclohexylmethane).

On the other hand, as the acid component monomer, for example, an alicyclic group such as 4,4'-diphenylmethane diisocyanate (MDI) or 1,3-bis (methyl isocyanate) cyclohexane (H6XDI) can be suitably used. , aliphatic diisocyanate, and the like.

In the above-described vapor deposition polymerization apparatus 20, when the protective film 7 made of a polymer is formed on the oxide dielectric film laminate 8 of the module 10, the valves 27a and 28a are closed. The pressure inside the vacuum chamber 22 is set to a high vacuum of about 3 × 10 ^-3 Pa, and the raw material monomers in the respective evaporation sources 25 and 26 are respectively heated to a specific temperature.

Next, after each raw material monomer reaches a specific temperature to obtain a desired evaporation amount, each of the valves 27a and 28a is opened to introduce the vapor of each raw material monomer into the vacuum chamber 22, and the steam of each raw material monomer is heated by the heater 29 to specify The evaporation rate guides each raw material monomer from above to the oxide dielectric film laminate 8 of the module 10 to be deposited.

In this case, the temperature of the module 10 on the stage 24 is controlled to a specific temperature by the temperature control means 23.

Thereby, a polymerization reaction is caused on the surface of the oxide dielectric film laminate 8 of the module 10, and the protective film 7 made of polyurea is entirely formed, whereby the protective film 7 covers the oxide dielectric film. The laminate 8 (see Fig. 2(b)).

Thus, in the case of this example, by-products, particularly hydrogen, are not generated during vapor deposition polymerization.

In the case of the present invention, the thickness of the protective film 7 composed of polyurea is not particularly limited, and it is considered to ensure desired insulating properties or mechanical properties. (especially the modulus of elasticity) is preferably 0.1 μm to 2.0 μm.

Fig. 4 is a view for explaining an example of the procedure of the second vapor deposition polymerization method.

In this example, a case where parylene is used as a specific organic material will be described as an example.

In this case, the p-xylene dimer is first prepared.

This p-xylene dimer is a solid and has the structure shown by the formula (1) of FIG.

In this example, in the process P1, the para-xylene dimer is vaporized by heating at a specific temperature.

Next, in the process P2, the vaporized p-xylene dimer is thermally decomposed by heating at a temperature higher than the aforementioned gasification step (process P1).

Thereby, a gas having a highly reactive radicalized p-xylene monomer is produced (see the formula (2) of FIG. 4).

Further, in the vapor deposition polymerization step of the process P3, the gas of the radicalized p-xylene monomer is guided to the oxide of the module 10 of the film formation object in a vacuum chamber (not shown). The dielectric thin film laminate 8 is deposited.

Moreover, it is not necessary to heat the module 10 to a high temperature during vapor deposition.

Thereby, a polymerization reaction is caused on the surface of the oxide dielectric film laminate 8 of the module 10, which is composed of a parylene represented by the formula (3) of FIG. 4 and a derivative of parylene. The protective film 7 is entirely formed into a film, whereby the protective film 7 covers the oxide dielectric film laminate 8 (see See Figure 2(b)).

Thus, in the case of this example, by-products, particularly hydrogen, are not generated during vapor deposition polymerization.

Further, the number n of the repetition units of the formula (3) of Fig. 4 is preferably 5,000 or more.

In the case of the present invention, the thickness of the protective film 7 composed of parylene is not particularly limited, and it is preferably 0.1 μm to 2.0 μm in consideration of securing desired insulating properties or mechanical properties (particularly, elastic modulus).

Thereafter, as shown in FIG. 2(c), the first contact hole 7a that communicates with the first electrode layer 4 is formed on the protective film 7 by a conventional photo-etching step, and is connected to the second electrode layer 6. The second contact hole 7b.

Next, as shown in FIG. 2(d), the first and second contact holes 7a and 7b are filled with metal materials 11, 12 made of, for example, aluminum.

Further, as shown in FIG. 2(e), a first extraction electrode 13 made of, for example, aluminum is provided on the upper portion of the first contact hole 7a, and is passed through the metal material 11 filled in the first contact hole 7a. The second extraction electrode 14 made of, for example, copper is provided on the upper portion of the second contact hole 7b, and is electrically connected to the metal material 12 filled in the second contact hole 7b. .

By the above steps, the intended oxide dielectric element 15 can be obtained (see FIG. 2(e)).

According to the present invention, since the elastic modulus of the protective film 7 composed of the polymer is extremely small compared to the cerium oxide of the ceramic, the piezoelectric characteristics can be greatly improved or the dielectric constant can be suppressed from being lowered.

Further, according to the present invention, in the vapor deposition polymerization, since by-products, particularly hydrogen, are not generated, the physical properties of the oxide dielectric layer 5 which are not deteriorated by reduction due to hydrogen ions are not caused.

Further, in the vapor deposition polymerization method of the present invention, since the vapor of the raw material monomer bypasses the periphery of the film formation object and undergoes a polymerization reaction on the surface of the film formation object, the oxide layer of the module 10 having the unevenness is used. The electric film laminate 8 can form the protective film 7 with excellent step coverage, whereby the insulation of the protective film can be improved as compared with the prior art.

[Examples]

Hereinafter, embodiments of the present invention will be specifically described together with comparative examples.

[Example 1]

The ruthenium substrate is prepared by sequentially forming a ruthenium oxide layer, a lower underlayer made of titanium, a first electrode layer made of platinum, an oxide dielectric layer made of a piezoelectric resin PZT, and platinum. An oxide dielectric thin film laminate body electrical module formed of a second electrode layer.

Here, the thickness of the oxide dielectric layer composed of PZT is 2 μm.

On the oxide dielectric film laminate of the module, a piezoelectric oxide dielectric is formed by a protective film made of polyurea having a total thickness of 1.0 μm by the first vapor deposition polymerization method. element.

The elastic film composed of the polyurea has a modulus of elasticity of 5 GPa.

Then, this piezoelectric oxidation is performed by conventional lithography techniques. The dielectric material element was formed into a cantilever shape to prepare a sample for evaluation of piezoelectric characteristics.

[Example 2]

A sample for evaluation of piezoelectric characteristics was produced in the same manner as in Example 1 except that a protective film made of polyurea having an elastic modulus of 10 GPa was formed.

[Comparative Example 1]

A sample for evaluation of piezoelectric characteristics was produced in the same manner as in Example 1 except that the protective film was not provided on the oxide dielectric film laminate of the piezoelectric module.

[Comparative Example 2]

A sample for evaluation of piezoelectric characteristics was produced in the same manner as in Example 1 except that a protective film of yttrium oxide was formed by a chemical vapor deposition (CVD) method instead of polyurea.

The elastic modulus of the protective film composed of this cerium oxide was 72 GPa.

<Evaluation of Piezoelectric Properties of Oxide Dielectric Elements>

With respect to the samples of Examples 1 and 2 and Comparative Examples 1 and 2, the piezoelectric constant was measured by applying an AC drive voltage having a frequency of 250 Hz and measuring the displacement amount of the cantilever using a laser Doppler vibrometer. The result is shown in Fig. 5.

<evaluation result>

As is understood from Fig. 5, in Example 1 in which a protective film made of polyurea having a thickness of 1.0 μm and an elastic modulus of 5 GPa was provided, the same piezoelectric constant as in Comparative Example 1 in which no protective film was provided was obtained.

On the other hand, in Example 2, in which the modulus of elasticity was as large as 10 GPa as compared with Example 1, the piezoelectric constant was somewhat reduced (about 5%), but it was still sufficiently practical.

On the other hand, in Comparative Example 2 in which a protective film made of ruthenium oxide was formed, the piezoelectric constant was relatively lower than in Examples 1 and 2.

Specifically, in Comparative Example 1 in which no protective film was provided, a decrease in piezoelectric constant of about 20% was observed.

From the above, the effects of the present invention can be demonstrated.

1‧‧‧矽 substrate (matrix)

2‧‧‧Oxide layer

3‧‧‧Underground

4‧‧‧1st electrode layer

5‧‧‧Oxide dielectric layer

6‧‧‧2nd electrode layer

7‧‧‧Protective film

7a‧‧‧1st contact hole

7b‧‧‧2nd contact hole

8‧‧‧Oxide dielectric thin film laminate

11, 12‧‧‧Metal materials

13‧‧‧1st take-out electrode

14‧‧‧2nd extraction electrode

Claims (6)

An oxide dielectric device comprising: a substrate; and an oxide dielectric thin film layered on the first and second electrode layers provided on the substrate and having an oxide dielectric layer interposed therebetween The oxide dielectric thin film layered body is covered with a protective film made of a polymer. The oxide dielectric component of claim 1, wherein the protective film is composed of polyurea. The oxide dielectric device of claim 1, wherein the protective film is composed of a derivative of parylene or parylene. The oxide dielectric device according to any one of claims 1 to 3, wherein the oxide dielectric layer is composed of lead zirconate titanate. The oxide dielectric device according to any one of claims 1 to 3, wherein the oxide dielectric layer is composed of lanthanum-niobium-titanium. A method for producing an oxide dielectric device, comprising: a substrate; and an oxide dielectric film layer provided on the substrate and having first and second electrode layers provided along an oxide dielectric layer The oxide dielectric thin film laminate is a method for producing an oxide dielectric device covered with a protective film made of a polymer, characterized in that it is prepared to have the oxide intercalation An oxide dielectric thin film layered body of the first and second electrode layers provided on the electric layer is provided on the substrate The module has a step of forming the protective film by an evaporation polymerization method.