JP5293347B2 - Composition for forming ferroelectric thin film, method for forming ferroelectric thin film, and ferroelectric thin film formed by the method - Google Patents

Description

  The present invention relates to a composition for forming a ferroelectric thin film suitable for use in a thin film capacitor having a high capacity density, a method for forming a ferroelectric thin film, and a ferroelectric thin film formed by the method.

  As a method of manufacturing this type of ferroelectric film, a mixed solution in which each component metal alkoxide or organic acid salt is dissolved in a polar solvent is used. It is generally known to form a dielectric thin film by heating to a temperature equal to or higher than the crystallization temperature and firing (see, for example, Patent Documents 1 and 2).

  However, when a thin film is used, there is a problem that a large stress due to the restraint of the substrate acts and a sufficient relative dielectric constant cannot be obtained (see, for example, Non-Patent Document 1).

  For this reason, attempts have been made to improve the dielectric constant by adding trace elements (see, for example, Non-Patent Document 2).

  In addition, since the electrostatic capacity is theoretically increased by reducing the thickness, attempts have been made to improve the electrostatic capacity by reducing the thickness.

JP-A-60-236404 (page 3, lower right column, line 11 to page 4, lower left column, line 10; page 5, upper right column, line 10 to same page, lower left column, line 17) JP-A-7-252664 (claims 2, 3, 7, 8, paragraphs [0001], [0035], [0117], [0118])

Ceramics, 42, 175-180 (2007) (p.175, left page, lines 20-22) SB Majumder, DC Agrawal, YN Mohopatra, and RS Katiyar, "Effect of Cerium Doping on the Microstructure and Electrical Properties of Sol-Gel Derived Pb1.05 (Zr0.53-dCedTi0.47) O3 (d = 10at%) Thin Films ", Materials Science and Engineering, B98, 2003, pp.25-32 (Fig.2)

  However, if the thickness of the formed ferroelectric thin film is reduced in order to increase the capacitance, the leakage current density increases and dielectric breakdown may occur. I couldn't do it. Moreover, it cannot be said that attempts to increase the relative dielectric constant by adding trace elements have been sufficiently performed.

  An object of the present invention is to provide a ferroelectric thin film forming composition suitable for high-capacity density thin film capacitor applications, which can significantly improve the relative permittivity over a conventional ferroelectric thin film by a simple method, and a ferroelectric It is an object to provide a method for forming a thin body film and a ferroelectric thin film formed by the method.

A first aspect of the present invention is a composition for forming a ferroelectric thin film for forming a ferroelectric thin film of PZT , wherein the general formula: ( Pb _x ) (Zr _z Ti _(1-z) ) O ₃ ( A mixed metal oxide A represented by 0.9 <x <1.3, 0 ≦ y <0.1, 0 < z <0.9) and mixed metal oxide B containing Nd A liquid composition for forming a thin film in the form of a composite metal oxide, wherein the raw material for constituting the composite metal oxide A and the raw material for constituting the composite metal oxide B are represented by the above general formula It is dissolved in the organic solvent so as to give a metal atomic ratio and the molar ratio B / A between B and A is in the range of 0.005 ≦ B / A <0.03. It consists of an organometallic compound solution.

  A second aspect of the present invention is an invention based on the first aspect, wherein the raw material for constituting the composite metal oxide A and the composite metal oxide B is an organic group via its oxygen or nitrogen atom. And a ferroelectric thin film forming composition which is a compound bonded to a metal element.

  The third aspect of the present invention is the invention based on the second aspect, and the raw materials for constituting the composite metal oxide A and the composite metal oxide B are metal alkoxide, metal diol complex, metal triol complex. For forming a ferroelectric thin film that is one or more selected from the group consisting of metal carboxylates, metal β-diketonate complexes, metal β-diketoester complexes, metal β-iminoketo complexes, and metal amino complexes It is a composition.

  A fourth aspect of the present invention is an invention based on the first to third aspects, further comprising a β-diketone, β-ketone acid, β-ketoester, oxyacid, diol, triol, higher carboxylic acid, alkanolamine And one or more stabilizers selected from the group consisting of polyamines and a ferroelectric further containing 0.2 to 3 moles per mole of the total amount of metals in the composition It is a composition for body thin film formation.

  According to a fifth aspect of the present invention, there is provided a step of applying a ferroelectric thin film forming composition based on the first to fourth aspects to a heat resistant substrate and heating in air, an oxidizing atmosphere, or a water-containing atmosphere. It is a method for forming a ferroelectric thin film characterized in that it is repeated once or until a film having a desired thickness is obtained, and the film is fired at a temperature equal to or higher than the crystallization temperature at least after heating in the final step.

  A sixth aspect of the present invention is a ferroelectric thin film formed by a method based on the fifth aspect.

Seventh aspect of the present invention is a thin film capacitor having a ferroelectric thin film based on the sixth aspect.

The composition for forming a ferroelectric thin film of the present invention has a general formula: ( Pb _x ) (Zr _z Ti _(1-z) ) O ₃ (where 0.9 <x <1.3, 0 ≦ y <0 .1 and 0 < z <0.9) are mixed in the organometallic compound solution so as to be in the form of a mixed composite metal oxide in which a composite metal oxide B containing Nd is mixed with the composite metal oxide A represented by The raw material for constituting the metal oxide A and the raw material for constituting the composite metal oxide B are in a predetermined ratio, and the molar ratio B / A between B and A is 0.005 ≦ B / A <0. 0.03 and dissolved in an organic solvent. By forming a ferroelectric thin film using this composition, a simple method for producing a ferroelectric thin film suitable for high-capacity density thin-film capacitor applications, in which the relative dielectric constant is significantly improved over conventional ferroelectric thin films There is an advantage that can be obtained.

  Next, the form for implementing this invention is demonstrated.

The composition for forming a ferroelectric thin film of the present invention is a composition for forming one kind of ferroelectric thin film selected from the group consisting of PLZT, PZT and PT. A ferroelectric thin film formed using this composition has a general formula: (Pb _x La _y ) (Zr _z Ti _(1-z) ) O ₃ (where 0.9 <x <1.3, 0 ≦ y <0.1, 0 ≦ z <0.9) takes the form of a mixed composite metal oxide in which a composite metal oxide B containing Nd is mixed with the composite metal oxide A. In the above equation, when y ≠ 0 and z ≠ 0, it is PLZT, when y = 0 and z ≠ 0, it is PZT, and when y = 0 and z = 0, it is PT. This composition has a ratio such that the raw material for constituting the composite metal oxide A and the raw material for constituting the composite metal oxide B give a metal atomic ratio represented by the above general formula, and B and It is dissolved in an organic solvent so that the molar ratio B / A with A is in the range of 0.005 ≦ B / A <0.03, and particularly preferably 0.005 ≦ B / A ≦ 0.02. It consists of an organometallic compound solution. If it is in the said range, a dielectric constant can be improved significantly rather than the conventional ferroelectric thin film. In addition, when it is less than the lower limit or exceeds the upper limit, the result is not much different from the case where no neodymium is added, and it is not suitable for high capacity density thin film capacitor applications.

  The raw material for composite metal oxide A and the raw material for composite metal oxide B are preferably compounds in which an organic group is bonded to each metal element of Pb, La, Zr, Ti and Nd via the oxygen or nitrogen atom. It is. For example, one kind selected from the group consisting of metal alkoxide, metal diol complex, metal triol complex, metal carboxylate, metal β-diketonate complex, metal β-diketoester complex, metal β-iminoketo complex, and metal amino complex Or 2 or more types are illustrated. Particularly suitable compounds are metal alkoxides, partial hydrolysates thereof, and organic acid salts. Among these, Pb compounds, La compounds, and Nd compounds include acetate (lead acetate, lanthanum acetate), 2-ethylhexanoate (neodymium 2-ethylhexanoate), 2-ethylbutyrate (neodymium 2-ethylbutyrate). ) And other organic acid salts, lead diisopropoxide, neodymium tetra n-butoxide, alkoxides such as neodymium ethoxide, and metal β-diketonate complexes such as tris (acetylacetonate) neodymium. Examples of the Ti compound include alkoxides such as titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, and titanium dimethoxydiisopropoxide. The Zr compound is preferably an alkoxide similar to the Ti compound. Although the metal alkoxide may be used as it is, a partially hydrolyzed product thereof may be used in order to promote decomposition.

  In order to prepare the composition for forming a ferroelectric thin film of the present invention, these raw materials are dissolved in an appropriate solvent at a ratio corresponding to the desired ferroelectric thin film composition, and prepared to a concentration suitable for coating.

  The solvent for the composition for forming a ferroelectric thin film used here is appropriately determined according to the raw material to be used. Generally, carboxylic acid, alcohol, ester, ketones (for example, acetone, methyl ethyl ketone), ether (E.g., dimethyl ether, diethyl ether), cycloalkanes (e.g., cyclohexane, cyclohexanol), aromatics (e.g., benzene, toluene, xylene), other tetrahydrofuran, or a mixture of two or more of these be able to.

  Specific examples of the carboxylic acid include n-butyric acid, α-methylbutyric acid, i-valeric acid, 2-ethylbutyric acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2- It is preferable to use ethylhexanoic acid or 3-ethylhexanoic acid.

  As the ester, ethyl acetate, propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, isobutyl acetate, n-amyl acetate, sec-amyl acetate, tert-amyl acetate, isoamyl acetate are used. As the alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol, 1-pentanol, 2-pentanol, 2-methyl-2-pentanol, 2-methoxy It is preferred to use ethanol.

  The total concentration of the organometallic compound in the organometallic compound solution of the ferroelectric thin film forming composition is preferably about 0.1 to 20% by weight in terms of metal oxide.

  In this organometallic compound solution, β-diketones (for example, acetylacetone, heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, benzoylacetone, etc.) are used as stabilizers as necessary. , Β-ketone acids (for example, acetoacetic acid, propionylacetic acid, benzoylacetic acid, etc.), β-ketoesters (for example, lower alkyl esters such as methyl, propyl, and butyl of the above ketone acids), oxyacids (for example, lactic acid, Glycolic acid, α-oxybutyric acid, salicylic acid, etc.), lower alkyl esters of the above oxyacids, oxyketones (eg, diacetone alcohol, acetoin, etc.), diols, triols, higher carboxylic acids, alkanolamines (eg, diethanolamine, Triethanolamine, Roh ethanolamine), a polyvalent amine or the like, may be added from 0.2 to 3 approximately at (stabilizer number of molecules) / (number of metal atoms).

  In the present invention, particles are removed from the prepared organometallic compound solution by filtration or the like, and the number of particles having a particle size of 0.5 μm or more (especially 0.3 μm or more, especially 0.2 μm or more) per 1 mL of the solution. It is preferable to be 50 / mL or less.

  If the number of particles having a particle size of 0.5 μm or more in the organometallic compound solution exceeds 50 particles / mL, the long-term storage stability becomes poor. The smaller the number of particles having a particle size of 0.5 μm or more in this organometallic compound solution, the more preferable, and particularly preferably 30 particles / mL or less.

  The method for treating the organometallic compound solution after preparation so as to achieve the number of particles is not particularly limited, and examples thereof include the following method. The first method is a filtration method in which a commercially available membrane filter having a pore size of 0.2 μm is used and pressure-fed with a syringe. The second method is a pressure filtration method in which a commercially available membrane filter having a pore size of 0.05 μm and a pressure tank are combined. The third method is a circulation filtration method in which the filter used in the second method and the solution circulation tank are combined.

  In any method, the particle capture rate by the filter varies depending on the solution pressure. It is generally known that the lower the pressure, the higher the capture rate. In particular, in the first method and the second method, the number of particles having a particle size of 0.5 μm or more is set to 50 or less. In order to achieve, it is preferable to pass the solution through the filter very slowly at low pressure.

  By using the composition for forming a ferroelectric thin film of the present invention, a mixed metal oxide B containing Nd is mixed with one kind of mixed metal oxide A selected from the group consisting of PLZT, PZT and PT A ferroelectric thin film in the form of a composite metal oxide can be easily formed.

  In order to form a ferroelectric thin film by using the composition for forming a ferroelectric thin film of the present invention, the composition is heat-resistant by a coating method such as spin coating, dip coating, or LSMCD (Liquid Source Misted Chemical Deposition). It apply | coats on a board | substrate and performs drying (temporary baking) and main baking.

As a specific example of the heat-resistant substrate to be used, a single crystal Si, polycrystalline Si, Pt, Pt (uppermost layer) / Ti, Pt (uppermost layer) / Ta, Ru, RuO ₂ , Ru ( Top layer) / RuO ₂ , RuO ₂ (top layer) / Ru, Ir, IrO ₂ , Ir (top layer) / IrO ₂ , Pt (top layer) / Ir, Pt (top layer) / IrO ₂ , SrRuO ₃ or _{(La x Sr (1-x} )) is a substrate with CoO ₃ perovskite-type conductive oxide such like, but not limited thereto.

  In addition, when a desired film thickness cannot be obtained by one application, the application and drying steps are repeated a plurality of times, followed by firing. Here, the desired film thickness refers to the thickness of the ferroelectric thin film obtained after the main firing, and in the case of a high capacity density thin film capacitor, the film thickness of the ferroelectric thin film after the main firing is 50 to 500 nm. Range.

  In addition, the preliminary calcination is performed in order to remove the solvent and thermally decompose or hydrolyze the organometallic compound to convert it into a composite oxide. Therefore, the calcination is performed in air, in an oxidizing atmosphere, or in a steam-containing atmosphere. Even in heating in the air, the moisture required for hydrolysis is sufficiently secured by the humidity in the air. This heating may be performed in two stages: low temperature heating for removing the solvent and high temperature heating for decomposing the organometallic compound.

The main firing is a step for firing and crystallizing the thin film obtained by the preliminary firing at a temperature equal to or higher than the crystallization temperature, and thereby a ferroelectric thin film is obtained. The firing atmosphere in this crystallization step is preferably O ₂ , N ₂ , Ar, N ₂ O, H _2, or a mixed gas thereof.

  Pre-baking is performed at 150 to 550 ° C. for about 5 to 10 minutes, and main baking is performed at 450 to 800 ° C. for about 1 to 60 minutes. The main baking may be performed by rapid heating treatment (RTA treatment). When the main baking is performed by the RTA treatment, the heating rate is preferably 10 to 100 ° C./second.

  The ferroelectric thin film of the present invention formed in this manner has a relative dielectric constant significantly improved as compared with the conventional ferroelectric thin film, has excellent basic characteristics as a capacitor, and has a high capacitance density. Suitable for use. The ferroelectric thin film of the present invention is also excellent in basic characteristics as an IPD.

  The ferroelectric thin film of the present invention includes a thin film capacitor, a capacitor, an IPD, a DRAM memory capacitor, a multilayer capacitor, a transistor gate insulator, a nonvolatile memory, a pyroelectric infrared detection element, a piezoelectric element, an electro-optical element, It can be used as a constituent material in composite electronic parts of actuators, resonators, ultrasonic motors, or LC noise filter elements. Among these, it can also be used especially for the thing corresponding to the frequency band of 100 MHz or more.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Examples 1-5>
First, zirconium tetra-n-butoxide and acetylacetone as a stabilizer were added to a reaction vessel, and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Titanium tetraisopropoxide and acetylacetone as a stabilizer were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Next, lead acetate trihydrate and propylene glycol as a solvent were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and further, propylene glycol was added and the concentration was adjusted to obtain a liquid containing a 30% by mass metal compound in terms of oxide. Furthermore, by adding diluted alcohol, a sol-gel solution containing a metal compound having a concentration of 10% by mass with a metal ratio of Pb / Zr / Ti = 110/52/48 in terms of oxide was obtained.

  Next, the sol-gel solution is divided into 5 equal parts, and 0.5 mol% of various neodymium compounds (2-ethylhexanoic acid neodymium, 2-ethylbutyric acid neodymium, neodymium triethoxide, neodymium tri-n-butoxide) are divided into these sol-gel liquids. And tris (acetylacetonate) neodymium) were added to obtain five types of thin film forming solutions.

Using these five types of thin film forming solutions, thin films were formed by the CSD method by the following method. That is, a 6-inch silicon substrate (Pt / TiO ₂ / SiO ₂ / Si (100) on which a Pt thin film was formed on the surface by a spin coating method at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. ) Substrate). Subsequently, using a hot plate, heating was performed at 350 ° C. for 5 minutes to perform temporary baking. This coating and pre-baking process was repeated 6 times, and then baked with an RTA (rapid heat treatment apparatus) at 700 ° C. for 1 minute in a 100% oxygen atmosphere to form a 270 nm thick ferroelectric thin film.

<Examples 6 to 10>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5 except that 1.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Examples 11 to 15>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5 except that 2.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Comparative Example 1>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5, except that the neodymium compound was not added to the sol-gel solution and the solution was used for forming a thin film.

<Comparative Examples 2-6>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 1 to 5 except that 3.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Examples 16 to 20>
First, zirconium tetra n-butoxide and diethanolamine as a stabilizer were added to a reaction vessel, and the mixture was refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Titanium tetraisopropoxide and diethanolamine as a stabilizer were added thereto, and the mixture was refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Next, lead acetate trihydrate and propylene glycol as a solvent were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and further, propylene glycol was added and the concentration was adjusted to obtain a liquid containing a 30% by mass metal compound in terms of oxide. Furthermore, by adding diluted alcohol, a sol-gel solution containing a metal compound having a concentration of 10% by mass with a metal ratio of Pb / Zr / Ti = 110/52/48 in terms of oxide was obtained.

  Next, the sol-gel solution is divided into 5 equal parts, and 0.5 mol% of various neodymium compounds (2-ethylhexanoic acid neodymium, 2-ethylbutyric acid neodymium, neodymium triethoxide, neodymium tri-n-butoxide) are divided into these sol-gel liquids. And tris (acetylacetonate) neodymium) were added to obtain five types of thin film forming solutions.

Using these five types of thin film forming solutions, thin films were formed by the CSD method by the following method. That is, a 6-inch silicon substrate (Pt / TiO ₂ / SiO ₂ / Si (100) on which a Pt thin film was formed on the surface by a spin coating method at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. ) Substrate). Subsequently, using a hot plate, heating was performed at 350 ° C. for 5 minutes to perform temporary baking. This coating and pre-baking process was repeated 6 times, and then baked with an RTA (rapid heat treatment apparatus) at 700 ° C. for 1 minute in a 100% oxygen atmosphere to form a 270 nm thick ferroelectric thin film.

<Examples 21 to 25>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 16 to 20, except that 1.0 mol% of various neodymium compounds were added to the sol-gel solution as an external solution to obtain a thin film forming solution.

<Examples 26 to 30>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 16 to 20 except that 2.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Comparative Example 7>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 16 to 20, except that the neodymium compound was not added to the sol-gel solution and the solution was used for forming a thin film.

<Comparative Examples 8-12>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 16 to 20, except that 3.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Examples 31-35>
First, zirconium tetra-n-butoxide and acetylacetone as a stabilizer were added to a reaction vessel, and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Titanium tetraisopropoxide and acetylacetone as a stabilizer were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Next, lead acetate trihydrate and propylene glycol as a solvent were added thereto and refluxed at a temperature of 150 ° C. in a nitrogen atmosphere. Thereafter, the by-product was removed by distillation under reduced pressure at 150 ° C., and further, propylene glycol was added and the concentration was adjusted to obtain a liquid containing a 30% by mass metal compound in terms of oxide. Furthermore, by adding diluted alcohol, a sol-gel solution containing a metal compound having a concentration of 10% by mass with a metal ratio of Pb / Zr / Ti = 110/52/48 in terms of oxide was obtained.

  Next, the sol-gel solution is divided into 5 equal parts, and 0.5 mol% of various neodymium compounds (2-ethylhexanoic acid neodymium, 2-ethylbutyric acid neodymium, neodymium triethoxide, neodymium tri-n-butoxide) are divided into these sol-gel liquids. And tris (acetylacetonate) neodymium) were added to obtain five types of thin film forming solutions.

Using these five types of thin film forming solutions, thin films were formed by the CSD method by the following method. That is, a 6-inch silicon substrate (Pt / TiO ₂ / SiO ₂ / Si (100) on which a Pt thin film was formed on the surface by a spin coating method at 500 rpm for 3 seconds and then at 3000 rpm for 15 seconds. ) Substrate). Subsequently, using a hot plate, heating was performed at 350 ° C. for 5 minutes to perform temporary baking. This coating and pre-baking process was repeated 6 times, and then baked in a dry air atmosphere at 700 ° C. for 1 minute with an RTA (rapid heat treatment apparatus) to form a 270 nm thick ferroelectric thin film.

<Examples 36 to 40>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 31 to 35 except that 1.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Examples 41 to 45>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 31 to 35 except that 2.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Comparative Example 13>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 31 to 35 except that the neodymium compound was not added to the sol-gel solution and the solution was used for forming a thin film.

<Comparative Examples 14-18>
A ferroelectric thin film was formed on the substrate in the same manner as in Examples 31 to 35, except that 3.0 mol% of various neodymium compounds were added to the sol-gel solution to obtain a thin film forming solution.

<Comparison evaluation>
About the board | substrate with which the ferroelectric thin film obtained in Examples 1-45 and Comparative Examples 1-18 was formed, about 250 micrometers square Pt upper electrode was produced with the sputtering method on the surface, and ferroelectric substance CV characteristics (voltage dependence of capacitance) are evaluated in the range of -5 to 5 V at a frequency of 1 kHz between the Pt lower electrodes directly under the thin film, and the relative dielectric constant εr is calculated from the maximum capacitance. did. In addition, HP measurement 4284A precision LCR meter was used for the measurement of CV characteristics, Bias step 0.1V, Frequency 1kHz, Oscillation level 30mV, Delay time 0.2sec, Temperature 23 ° C, Hygrometer 10 conditions. Measured with The results are shown in the following Tables 1 to 3, respectively.

表１〜表３から明らかなように、Ｎｄを含まない比較例１，７，１３のＰＺＴ強誘電体薄膜に比べて、Ｎｄを０．５％〜２％添加した実施例１〜４５の強誘電体薄膜では、２７０ｎｍ程度の薄い膜厚で、高い静電容量及び高い比誘電率が確認された。この結果から、実施例１〜４５の強誘電体薄膜は、キャパシタとしての基本的特性が優れていることが判った。

As is apparent from Tables 1 to 3, compared with the PZT ferroelectric thin films of Comparative Examples 1, 7, and 13 that do not contain Nd, the strengths of Examples 1 to 45 in which 0.5% to 2% of Nd was added. In the dielectric thin film, a high capacitance and a high relative dielectric constant were confirmed with a thin film thickness of about 270 nm. From this result, it was found that the ferroelectric thin films of Examples 1 to 45 were excellent in basic characteristics as a capacitor.

  However, the ferroelectric thin films of Comparative Examples 2-6, 8-12, and 14-18 to which 3% of Nd was added had lower results than the PZT ferroelectric thin films of Comparative Examples 1, 7, and 13 that did not contain Nd. It is had.

  Further, from the results of the ferroelectric thin films of Examples 1 to 45 and Comparative Examples 2 to 6, 8 to 12, and 14 to 18 in which the addition amount of Nd was changed, Examples 6 to 10, 21 to 1% added were added. The results of 25, 36 to 40 were particularly high. Next, Examples 1 to 5, 16 to 20, 31 to 35 added with 0.5%, and Examples 11 to 15, 26 to 30, 41 added with 2% were added. The results of 45 were almost the same results, and the results of Comparative Examples 2-6, 8-12, 14-18 added with 3% were low results.

  From this result, it was confirmed that there is an appropriate range of Nd addition amount that can contribute to the improvement of the capacitance and the relative dielectric constant εr.

  The composition for forming a ferroelectric thin film of the present invention, the method for forming a ferroelectric thin film, and the ferroelectric thin film formed by the method are excellent in basic characteristics as a capacitor, and are used for a high-capacity density thin film capacitor. Is available. In addition, it has excellent basic characteristics as an IPD. IPD, DRAM memory capacitor, multilayer capacitor, transistor gate insulator, nonvolatile memory, pyroelectric infrared detector, piezoelectric element, electro-optical element, actuator, resonator It can be used for composite electronic parts such as ultrasonic motors or LC noise filter elements.

Claims (7)

In a composition for forming a ferroelectric thin film for forming a ferroelectric thin film of PZT ,
General formula: ( Pb _x ) (Zr _z Ti _(1-z) ) O ₃ (wherein 0.9 <x <1.3, 0 < z <0.9) A liquid composition for forming a thin film in the form of a mixed composite metal oxide mixed with a composite metal oxide B containing Nd,
The raw material for constituting the composite metal oxide A and the raw material for constituting the composite metal oxide B are in such a ratio that gives the metal atomic ratio represented by the above general formula, and the moles of B and A A composition for forming a ferroelectric thin film comprising an organometallic compound solution dissolved in an organic solvent such that the ratio B / A is in the range of 0.005 ≦ B / A <0.03 object.   2. The ferroelectric thin film formation according to claim 1, wherein the raw material for constituting the composite metal oxide A and the composite metal oxide B is a compound in which an organic group is bonded to a metal element via its oxygen or nitrogen atom. Composition.   The raw materials for constituting the composite metal oxide A and the composite metal oxide B are metal alkoxide, metal diol complex, metal triol complex, metal carboxylate, metal β-diketonate complex, metal β-diketoester complex, metal β The composition for forming a ferroelectric thin film according to claim 2, wherein the composition is one or more selected from the group consisting of an iminoketo complex and a metal amino complex.   Composition of one or more stabilizers selected from the group consisting of β-diketone, β-ketone acid, β-ketoester, oxyacid, diol, triol, higher carboxylic acid, alkanolamine and polyvalent amine The composition for forming a ferroelectric thin film according to any one of claims 1 to 3, further comprising 0.2 to 3 moles per mole of the total amount of metals in the product.   5. A process of applying the ferroelectric thin film forming composition according to claim 1 to a heat resistant substrate and heating in air, in an oxidizing atmosphere or in a water-containing atmosphere once or as desired. A method for forming a ferroelectric thin film, which is repeated until a film having a thickness is obtained, and the film is fired at a temperature equal to or higher than a crystallization temperature at least during or after heating in the final step.   A ferroelectric thin film formed by the method according to claim 5. Thin film capacitor having a ferroelectric thin film according to claim 6, wherein.