JP4883293B2 - Method for manufacturing composition for forming ferroelectric film and method for manufacturing ferroelectric film - Google Patents

Description

The present invention relates to a method of manufacturing a relatively low temperature manufacturing process and the ferroelectric film of the ferroelectric film forming composition capable of forming a ferroelectric film by MOD process in baking.

  A ferroelectric film including a crystal typified by lead zirconate titanate (PZT) has spontaneous polarization, high dielectric constant, electro-optic effect, piezoelectric effect, pyroelectric effect, etc. It is applied to a wide range of device development. As a method for forming such a ferroelectric film, for example, there is a chemical solution deposition method such as a sol-gel method and a MOD (Metal Organic Deposition) method.

  The sol-gel method is a method of forming a precursor by forming a three-dimensional structure of MOM by hydrolysis and polycondensation of an organometallic compound such as a metal alkoxide. However, since the reaction proceeds with moisture in the air, there is a problem that the stability is low and it is very difficult to manage the solution for the sol-gel method. On the other hand, the MOD method is a method for obtaining a ferroelectric film by simply applying, drying, degreasing and firing a solution of an organometallic compound without causing a gelation reaction (hydrolysis reaction). Can be made into a very stable solution by allowing a stable organometallic compound such as a metal carboxylate to exist in a molecular state, but there is a problem that firing at a relatively high temperature is required.

  As a solution to this problem, there is a method in which the sol-gel method is improved and a solution for the MOD method is mixed with the solution for the sol-gel method (see Patent Document 1). In the method described in this document, a solution for the MOD method and a solution for the sol-gel method that can be fired at a relatively low temperature are mixed and used, so that the solution for the MOD method is used alone. A dense film can be obtained by firing at a lower temperature than in the case.

Japanese Patent Laying-Open No. 2005-306711 (Claims etc.)

  However, since the solution of Patent Document 1 uses a solution for the sol-gel method, there is a problem that the stability of the solution is not sufficient.

That the present invention has been made in view of such circumstances, to provide a method of the production method and the ferroelectric film of the ferroelectric film forming composition capable of forming a ferroelectric film by MOD process at a low temperature of firing With the goal.

The manufacturing method of the composition for forming a ferroelectric film of the present invention that solves the above-mentioned problems is a colloidal solution prepared by mixing a metal compound other than lead and zirconium , lead acetate and zirconium acetylacetonate in a solvent at room temperature and heating. The composition for forming a ferroelectric film for forming a ferroelectric film by the MOD method is allowed to stand for 12 hours to less than 25 days in an environment of 5 to 15 ° C. Te, lead (Pb) and zirconium (Zr) and an organometallic compound containing a methyl group and carboxylate group in the same molecule, the ferroelectric film forming composition containing a compound of a metal other than lead and zirconium It is characterized by obtaining .
According to this, for forming a ferroelectric film containing lead (Pb), zirconium (Zr), an organometallic compound containing a methyl group and a carboxylate group in the same molecule, and a compound of a metal other than lead and zirconium A composition can be reliably formed. The composition for forming a ferroelectric film produced by the method for producing a composition for forming a ferroelectric film of the present invention comprises an organometallic compound having Pb, Zr, methyl group and carboxylate group in the same molecule. Because it contains, by applying, drying, degreasing, and firing this composition for forming a ferroelectric film, compared to the case of using a composition for forming a ferroelectric film having Pb and Zr in different molecules, Since crystallization of the ferroelectric film component can proceed with low energy, a ferroelectric film having Pb and Zr can be formed by firing at a low temperature. Further, since it is a composition for forming a ferroelectric film for the MOD method, it does not react with moisture in the air as in the case of a composition for forming a ferroelectric film for the sol-gel method. And a stable composition for forming a ferroelectric film.

Furthermore, it is preferable that the organometallic compound is contained as fine crystals of 0.1 μm or less.
According to this, a composition for forming a ferroelectric film containing an organometallic compound containing Pb, Zr, —CH _3, and —COO— as microcrystals of 0.1 μm or less is obtained, which is dense even when fired at low temperature. A ferroelectric film can be obtained.

Also, after a titanium tetra iso pro Pokishido and diethanolamine as a compound of a metal other than the lead and zirconium were mixed into the solvent, it is preferable to mix the lead acetate and the zirconium acetylacetonate.
According to this, a ferroelectric film forming composition capable of forming a PZT film by a MOD method by firing at a low temperature can be provided.

The method for producing a ferroelectric film according to the present invention comprises producing a composition for forming a ferroelectric thin film by the method for producing a composition for forming a ferroelectric film, and applying the produced composition for forming a ferroelectric thin film. The ferroelectric film is formed by coating on an object, drying and degreasing it, and firing.
According to this, since the ferroelectric film can be formed by low-temperature firing, it is possible to suppress the influence on the object or the like due to heating.

Hereinafter, the present invention will be described in detail based on embodiments.
The composition for forming a ferroelectric film of the present invention is a colloidal solution used to form a ferroelectric thin film by the MOD method. Specifically, lead (Pb), zirconium (Zr), and a methyl group ( It contains an organometallic compound containing —CH ₃ ) and a carboxylate group (—COO—), and a compound of a metal other than lead and zirconium.

The composition for forming a ferroelectric film of the present invention for such a MOD method is a temperature lower than a baking temperature of 700 to 750 ° C. in a general MOD method, for example, about 650 to 700 ° C. lower by about 50 ° C. The ferroelectric film can be formed by crystallization. This is presumably because the organometallic compound containing —CH ₃ and —COO— contained in the composition for forming a ferroelectric film of the present invention has both Pb and Zr.

More specifically, in the present invention, the organometallic compound containing —CH ₃ and —COO— contained in the composition for forming a ferroelectric film has Pb and Zr in the same molecule. An oxide of a Pb—Zr alloy is formed by applying, drying, and degreasing the composition for forming a dielectric film on an object such as a substrate. In addition, oxides of metals other than lead and zirconium are also formed. Then, by subsequent firing, an oxide of a metal other than lead and zirconium is dissolved in the oxide of the Pb—Zr alloy and crystallized to form a ferroelectric film.

  On the other hand, in the composition for forming a ferroelectric film in which Pb and Zr are not in the same compound but in different compounds, lead oxide and zirconium oxide are separately formed by coating, drying, and degreasing, and then oxidized by oxidation. Lead, zirconium oxide, and oxides of metals other than lead and zirconium are dissolved and crystallized at a time to form a ferroelectric film.

  Therefore, when the former composition for forming a ferroelectric film of the present invention is used as energy for crystallization to form a ferroelectric film, the latter ferroelectric film exists in a compound having different Pb and Zr. Since it becomes lower than the case where the forming composition is used, the ferroelectric film-forming composition of the present invention can be used to form a ferroelectric film having Pb and Zr by firing at a relatively low temperature. It is guessed.

Specifically, in the present invention, for example, when a compound of a metal other than lead and zirconium is a titanium compound (denoted as “Ti—R ′” in the following formula. R ′ is an alkyl group), By applying, drying and degreasing the composition for forming a ferroelectric film of the present invention to an object, an organometallic compound containing Pb, Zr, —CH ₃ and —COO— as shown in the following reaction formula ( In the following formula, “PbZr—R”) represents an oxide of a Pb—Zr alloy, and the titanium compound becomes a titanium oxide.

Thereafter, by firing, TiO _y is dissolved in PbZrO _x and crystallized. This crystallization is performed when a composition for forming a ferroelectric film in which Pb and Zr are not in the same compound but in different compounds, that is, PbO _a (0.1 ≦ a ≦ 1), ZrO _b (0 0.1 ≦ b ≦ 2) and TiO _c (0.1 ≦ c ≦ 2) are solid solution crystallized at a lower energy than in the case of solid solution at a time. Therefore, it is presumed that the ferroelectric film forming composition of the present invention can form a ferroelectric film having Pb and Zr by firing at a relatively low temperature.

The organometallic compound containing Pb, Zr and -CH ₃ and -COO- the contains Pb and Zr, for example, can be confirmed by EDX measurement of organometallic compound. Since the organometallic compound is minute, for example, as shown in the following test examples, the composition for forming a ferroelectric film of the present invention is allowed to stand for 25 days or more in an environment of 5 to 15 ° C. Can be confirmed by measuring the EDX of the grown product.

The organometallic compound containing Pb, Zr, —CH ₃ and —COO— contained in the composition for forming a ferroelectric film of the present invention is 770, 847, 929, 953, 1022, 1125 in FT-IR spectrum measurement. 1279, 1333, 1415, 1508, 1579, 2862, 2914, 2964, 3193, 3276, and 3411 cm ^{−1 in the} vicinity. Specifically, it is preferable that the spectrum is substantially the same as the FT-IR spectrum shown in FIG. It should be noted that 770, 847, 929, 953, 1022, 1125, 1279, 1333, 1415, 1508, 1579, 2862, 2914, 2964, 3193, 3276, and 3411 cm ⁻¹ , even in the case of organometallic compounds having these peaks, these wave numbers , That is, an organic metal compound having a peak within an error range in normal FT-IR spectrum measurement, for example, within a range of ± 5 cm ⁻¹ . As in the above EDX measurement, for example, as shown in the following test examples, the composition for forming a ferroelectric film of the present invention is allowed to stand for 25 days or more in an environment of 5 to 15 ° C. to grow an organometallic compound. The FT-IR spectrum of the organometallic compound containing Pb, Zr, —CH _3, and —COO— contained in the composition for forming a ferroelectric film of the present invention is confirmed by performing FT-IR measurement on the obtained product. Can do.

In the composition for forming a ferroelectric film of the present invention, the organometallic compound containing Pb, Zr, —CH ₃ and —COO— is contained as a microcrystal having a size of 0.1 μm or less. preferable. The size of the microcrystal can be measured by SEM observation, and “microcrystal of 0.1 μm or less” means that the long side of the crystal observed by SEM is 0.1 μm or less. .

  Examples of the metal compound other than lead and zirconium include titanium alkoxide and titanium isopropoxide. In addition, although the compounding ratio of the compound of metals other than Pb, Zr, and Pb and Zr is not specifically limited, For example, when manufacturing the composition for ferroelectric thin film formation which consists of lead zirconate titanate (PZT), for example. Pb: Zr: Ti = 1.0 to 1.2: 0.50 to 0.55: 0.45 to 0.50 (molar ratio) is preferable.

  As a solvent (dispersion medium) of the composition for forming a ferroelectric film of the present invention, butyl cellosolve, 2-n-butoxy alcohol, n-pentyl alcohol, 2-phenylethanol, 2-phenoxyethanol, methoxyethanol, ethylene glycol monoacetate And alcohol solvents such as triethylene glycol, trimethylene glycol, propylene glycol, neopentyl glycol, isoamyl acetate and the like. These solvents may be used alone or in combination.

  The composition for forming a ferroelectric film of the present invention preferably further contains alkanolamines. When amines are contained, the dispersion stability of each component is improved. Examples of amines include alkanolamines such as monoethanolamine and diethanolamine. These amines may be used alone or in combination.

  Furthermore, polyethylene glycol or the like may be contained as necessary as a stabilizer for stabilizing each component or preventing the occurrence of cracks in the formed ferroelectric film. Moreover, you may add a thickener etc. as another additive.

  The composition for forming a ferroelectric film of the present invention is formed by mixing a metal compound other than lead and zirconium, lead acetate and zirconium acetylacetonate in a solvent at room temperature and heating to form a colloidal solution. This colloidal solution can be produced by allowing it to stand for 12 hours or more and less than 25 days in an environment of 5 to 15 ° C.

First, at room temperature (20-25 ° C.), a compound of lead and a metal other than zirconium and titanium tetra iso pro Pokishido, lead acetate, a zirconium acetylacetonate, mixed in a solvent such as an alcohol solvent. Thereafter, the mixed liquid is heated to form a colloidal solution. The heating temperature is not limited, and is, for example, 70 to 80 ° C. Also, the heating time is not particularly limited, and can be set to a time suitable for the amount and type of the target ferroelectric film forming composition. For example, it may be about 30 to 60 minutes.

  Thereafter, the colloidal solution is allowed to stand in an environment of 5 to 15 ° C., preferably around 10 ° C., for 12 hours or more and less than 25 days, preferably 1 to 14 days. Thus, the ferroelectric film-forming composition of the present invention can be obtained by refrigeration at a predetermined temperature for a predetermined period.

  It is preferable to add alkanolamines such as diethanolamine. Moreover, you may add polyethyleneglycol etc. as an additive after a heating as needed. Furthermore, you may add a thickener etc. as another additive.

The order of mixing the components is not particularly limited, after mixing alkanolamines such as lead and compounds of metals other than zirconium and diethanolamine, such as titanium tetra iso pro Pokishido in a solvent, mixing lead acetate and zirconium acetylacetonate It is preferable to do. By mixing in this order, metal compounds other than lead and zirconium are chelated with alkanolamines in an alcohol solvent in advance, so that the stability of metal compounds other than lead and zirconium is reliably improved. It is.

  The mixing ratio of lead acetate, zirconium acetylacetonate, and a compound of a metal other than lead and zirconium is not particularly limited. For example, a ferroelectric thin film forming composition comprising lead zirconate titanate (PZT) is used. When producing, lead acetate, zirconium acetylacetonate so that Pb: Zr: Ti = 1.0 to 1.2: 0.50 to 0.55: 0.45 to 0.50 (molar ratio). And a titanium compound are preferably mixed.

  A ferroelectric film can be produced by applying such a composition for forming a ferroelectric film onto an object such as a silicon substrate, drying and degreasing the composition, and firing the composition. Since the composition for forming a ferroelectric film of the present invention can lower the firing temperature than a general MOD method, the influence of heating on the object can be suppressed. In the step of applying the ferroelectric film forming composition on the object, dry inert gas is introduced at a predetermined flow rate into the tank in which the ferroelectric film forming composition is stored, and the ferroelectric film is formed. It is preferable that the body film forming composition is transported to a nozzle connected to the tank and the ferroelectric film forming composition is dropped onto the rotating object from the nozzle. Thereby, a precursor film of a ferroelectric film in which film components are dispersed substantially uniformly can be manufactured relatively easily.

  The ferroelectric film formed by using the ferroelectric film forming composition of the present invention described above can be applied to a wide range of device development, and its use is not particularly limited. , Filter, delay line, lead selector, tuning fork oscillator, tuning fork clock, transceiver, piezoelectric pickup, piezoelectric earphone, piezoelectric microphone, SAW filter, RF modulator, resonator, delay element, multistrip coupler, piezoelectric accelerometer, piezoelectric speaker, etc. It can be applied to.

Hereinafter, it demonstrates still in detail based on an Example.
(Example)
In an inert gas (nitrogen), 354 g of butyl cellosolve (CH ₃ (CH ₂ ) ₃ OCH ₂ CH ₂ OH) as a dispersion medium and titanium tetraisopropoxide (Ti ((CH ₃ ) ₂ CHO) ₄ ) 41.8 g And 75 g of diethanolamine (HN (CH ₂ CH ₂ OH) ₂ ) were mixed with stirring. Thereafter, 136.3 g of lead acetate trihydrate (Pb (CH ₃ COO) ₂ .3H ₂ O) and zirconium acetylacetonate (Zr (CH ₃ COCHCOCH ₃ ) ₄ ) 76.6 g in air are further added at room temperature. After stirring and mixing, the mixture was heated and stirred at 70 ° C. for 30 minutes to dissolve each component to prepare a colloidal solution. Next, after cooling to 30 ° C. or lower, 34.2 g of polyethylene glycol (average molecular weight 400) was stirred and mixed as a crack preventing agent. Thereafter, this solution was allowed to stand in an environment of 10 ° C. for 10 days to obtain a ferroelectric film forming composition. When this composition for forming a ferroelectric film was observed with an SEM, crystals larger than 0.1 μm were not observed.

  Next, the obtained composition for forming a ferroelectric film was applied onto a silicon substrate, dried and degreased, and then fired at 650 ° C. As a result, crystallization proceeded well and a dense PZT film was obtained. .

(Test example)
The composition for forming a ferroelectric film of the example was further allowed to stand in an environment of 10 ° C. for 20 days (30 days in total) to grow and deposit fine particles contained in the composition for forming a ferroelectric film. . The result of SEM observation of the precipitated crystal is shown in FIG. 1, and the result of EDX analysis is shown in FIG. As a result, the observed crystal was found to be an organometallic compound having Pb and Zr. Moreover, the result of having analyzed this deposited crystal | crystallization by FT-IR is shown in FIG. As a result, it was found that the precipitate contained a methyl group (—CH ₃ ) and a carboxylate group (—COO—). The main FT-IR absorption wavelengths are 769.8, 847.3, 928.9, 952.9, 1021.8, 1124.9, 1279.4, 1333.0, 1415.0, 1508.3. 1579.0, 2861.5, 2913.7, 2964.3, 3193.4, 3276.0, 3411.2 cm ⁻¹ .

From these results, it was found that the composition for forming a ferroelectric film of the example contains an organometallic compound having Pb, Zr, —CH ₃ and —COO—. In addition, the FT-IR spectrum of lead acetate trihydrate is shown in FIG. 4, the FT-IR spectrum of zirconium acetylacetonate is shown in FIG. 5, and FIGS. As can be seen from these figures, the composition for forming a ferroelectric film of the present invention comprises an organometallic compound having an FT-IR spectrum different from that of the raw material and having Pb, Zr, —CH ₃ and —COO—. It was confirmed that it contained.

SEM observation results of crystals precipitated by further refrigeration of the composition for forming a ferroelectric film Results of EDX measurement of crystals precipitated by further refrigeration of the composition for forming a ferroelectric film Results of FT-IR measurement of crystals deposited by further refrigeration of the composition for forming a ferroelectric film FT-IR spectrum of lead acetate trihydrate FT-IR spectrum of zirconium acetylacetonate The figure which combined FT-IR spectrum of FIGS.

Claims (4)

A compound of a metal other than lead and zirconium, lead acetate and zirconium acetylacetonate are mixed in a solvent at room temperature and heated to form a colloidal solution, and then the colloidal solution is subjected to an environment of 5 to 15 ° C. for 12 hours to 25 days. by less than stand, strong dielectric film a ferroelectric film forming composition for forming by the MOD method, lead (Pb) and zirconium (Zr) and the same of methyl groups and carboxylate groups A method for producing a composition for forming a ferroelectric film comprising obtaining a composition for forming a ferroelectric film comprising an organometallic compound contained in a molecule and a compound of a metal other than lead and zirconium . The method for producing a composition for forming a ferroelectric film according to claim 1 , wherein the organometallic compound is contained as fine crystals of 0.1 μm or less. After mixing the titanium tetra iso pro Pokishido diethanolamine as the compound in the solvent, the ferroelectric film formed according to claim 1 or 2, characterized in that mixing the lead acetate and the zirconium acetylacetonate A method for producing a composition. A ferroelectric thin film forming composition is manufactured by the method for manufacturing a ferroelectric film forming composition according to any one of claims 1 to 3, and the manufactured ferroelectric thin film forming composition is coated. A method for producing a ferroelectric film, comprising: applying the product onto an object, drying the powder, and baking the product after being degreased to form the ferroelectric film.

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