JPS59220913A - Titanium zirconate lead dielectric thin film and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides dielectric thin films, particularly those having a thickness of 1000 to 1500 mm.
This invention relates to a lead titanium zirconate dielectric thin film and a method for producing the same.

Dielectric films are conventionally made by pressure molding a powdery dielectric composition.
Although it is manufactured by sintering, it is extremely difficult to manufacture a thin film with a thickness of less than 10 microns and a high dielectric constant using this method, which is a condition for an excellent thin film capacitor. Furthermore, since the sintering temperature is extremely high, expensive metals must be used as electrodes. Spackling method, vacuum evaporation method, gas phase reaction method, etc. are being considered as methods for manufacturing dielectric thin films suitable for excellent thin film capacitors, but it is extremely difficult to control the stochiometry with these methods. Furthermore, since only extremely thin films can be obtained, electrical conduction is likely to occur, so that this method has not been put to practical use. Apart from these methods, a solution containing an organometallic compound is applied onto a glass substrate by a dropping method or a dipping method, and is then dried in air at room temperature for 30 minutes and then in a constant temperature bath at 110°C for 30 minutes for hydrolysis. After the reaction is completed, a method of manufacturing a dielectric thin film by heating and baking at a temperature of 200°C to 800°C while forcibly introducing water vapor in an electric furnace is disclosed in JP-A-56-28.
This is proposed in Publication No. 408. However, in this method, it is difficult to obtain a homogeneous coating film because the exemplified organometallic compound solution absorbs moisture in the atmosphere and is easily hydrolyzed and is extremely unstable. In addition, because it is extremely difficult to control the atmosphere during hydrolysis and heating and baking, especially the water vapor partial pressure, defects such as cranks and pinholes occur in the formed thin film, resulting in conduction, resulting in poor electrical properties. In particular, it is difficult to obtain a dielectric thin film having dielectric properties, and the publication does not specifically describe the electrical properties.

Generally, in order to obtain a high relative permittivity, it is necessary to crystallize the dielectric composition, but in the case of thin films, conduction due to grain boundaries occurs due to crystallization of the thin film composition, so a high relative permittivity is required. It is generally accepted that it is not possible to obtain a dielectric thin film with the same characteristics.

The present invention has a high dielectric constant and a film thickness of 1000 to 1
The object of the present invention is to provide a homogeneous and transparent lead titanium zirconate dielectric thin film and a method for manufacturing the same.

As a result of intensive research to achieve the above object, the present inventors applied an acetylacetone solution of a titanium-zirconium-lead composite organometallic compound onto a heat-resistant substrate as a precursor solution for forming lead titanium zirconate and heated it. The inventors have completed the present invention by discovering that a laminate of lead titanium zirconate thin films obtained by firing, repeating coating and heating and firing has a high dielectric constant.

The present invention relates to a lead titanium zirconate dielectric thin film, characterized in that it is formed by laminating a lead titanium zirconate thin film represented by the compositional formula % (1) in multiple layers on a heat-resistant substrate, and its production. It's a method.

In the present invention, the titanium lead zirconate dielectric thin film has a composition formula of txtP with a thickness of several hundred to three thousand people.
b (Zrx' Tiy) 03-・"="' (
1) (where X is 0.7 to 0.45, y is 0.3 to 0.55, and x+y=l) A lead titanium zirconate thin film expressed as ～The total thickness is 1000～ by laminating 10 layers.
It is a transparent thin film body of 15,000A, and although it varies depending on the number of laminated layers and total thickness, the relative dielectric constant: ε is 450 to 550, the dielectric loss: tan δ is 0.05 to O, Ite, and the specific resistance is has electrical properties on the order of 10"0 Ω. If the composition of the lead titanium zirconate thin film is outside the above range, it is not preferable because the above electrical properties cannot be obtained.

In the present invention, the titanium lead zirconate dielectric thin film is produced by a β-diketone solution of a mixture of an organic titanium compound, an organic zirconium compound, and a lead compound in a predetermined ratio, or a composite organic metal obtained by reacting these. A β-diketone solution of the compound is applied as a precursor solution for producing lead titanium zirconate on a heat-resistant substrate, and then heated and baked to form a lead titanium zirconate IJ film, and the precursor solution is applied and heated and baked. Manufactured by repeating.

As the organic titanium compound, any compound can be used as long as it is soluble in β-diketone. for example,
Tetraethoxytitanium, tetraisopropoxytitanium,
Tetrabutoxytitanium alkoxides and polymers produced by their hydrolysis, some or all of the alkoxy groups of titanium alkoxides are replaced with β-acetylacetone, hendiylacetone, etc.
diketones, ketone acids such as ace1-acetic acid, propionylbutyric acid, and benzoylformic acid, lower alkyl esters of said ketone acids, lactic acid, and glycolic acid.

α-oxybutyric acid. Chelation of oxyacids such as salicylic acid, lower alkyl esters of the oxyacids, oxyketones such as diacetone alcohol and acetate, α-amic acids such as glycine and alanine, amino alcohols such as aminoethyl alcohol, etc. Mention may be made of titanium alkoxide derivatives substituted with residues of agents. Further, as the organic zirconium compound, a compound having the same type of substituent as the organic titanium compound can be used. As the lead compound, inorganic compounds such as lead oxide, lead hydroxide, and lead chloride, and lead carboxylates such as lead acetate can be used.

In the present invention, a solution of β-diketone, such as acetylacetone or benzoylacetone, which is a mixture of the above-described organic titanium compound, an organic zirconium compound, and a lead compound in a predetermined ratio, or a solution of an organic titanium compound, an organic zirconium compound, and a lead compound, such as acetylacetone, benzoylacetone, etc. A lead-containing composite organometallic compound obtained by reacting the following in a predetermined ratio, preferably a lead-containing complex organometallic compound obtained by reacting titanium alkoxide, zirconium alkoxide, and lead carboxylate as proposed by the present applicant in JP-A-58-41723. compositional formula (2)%
Formula % (2) (wherein, the gates are titanium and zirconium atoms R and R represent the same or different alkyl or aryl groups, m and n are 0.1 or 2, and m+n is 2 The β-diketone solution of the lead-containing complex organometallic compound represented by .) is used as a precursor solution for producing lead titanium zirconate. The concentration of the metal compound in the precursor solution is 5 to 5 in terms of complex metal oxide, that is, lead titanium zirconate.
The ratio is 20%. If the concentration of the metal compound is too low, the thickness of the lead titanium zirconate thin film formed by one coating and heating and baking will be too thin, and the number of repetitions of coating and heating and baking will have to be increased, and it will also be too high. This is not preferable because the coating thickness of the precursor formed by one application becomes thick and cracks are likely to occur during heating and baking.

In addition to β-diketone, methanol and efnol were used as solvents.

Lower alcohols such as isopropanol and butanol,
Lower esters such as methyl formate, methyl acetate, ethyl acetate, methyl acetoacetate, and methyl acetoacetate can also be used, but β-diketones are preferred from the viewpoint of stability of the precursor solution.
Particularly preferred is acetylacetone.

In the present invention, a glass plate, a ceramic plate, a glass plate coated with a conductive i-film, a metal plate, a metal foil, etc. are used as the heat-resistant substrate on which the lead titanium zirconate thin film is formed. can. Any known coating method such as a dipping method, a spray method, a spinner method, a printing method, or a brush coating method can be used to apply the precursor solution onto the heat-resistant substrate. A dipping method is preferred because it can easily produce a homogeneous coating film, and dipping is performed while maintaining the temperature of the precursor solution at 40 to 95°C.
The dipping method is more preferred. The heating and firing temperature of the heat-resistant substrate coated with the precursor solution varies depending on the type and concentration of the metal compound in the precursor solution, the type of solvent, the type of the heat-resistant substrate, etc., but is at least the crystallization temperature of lead titanium zirconate. It is necessary to heat to a temperature of 450-800℃,
Preferably it is 500-700°C.

The lead titanium zirconate dielectric thin film of the present invention is manufactured to have a predetermined total thickness by repeating the application of the precursor solution and heating and baking a plurality of times. The number of repetitions of coating and heating and baking is 2 to 10 times, preferably 5 to 10 times.

If the coating is applied and fired once, thin film defects such as pinholes remain and conduction occurs, and if the coating is repeated 10 times or more, no further improvement in electrical properties is observed, which is not preferable.

The titanium lead zirconate dielectric thin film of the present invention has the electrical properties described above and can be used not only as a thin film capacitor but also as a pyroelectric material and a piezoelectric material.

The reason why the lead titanium zirconate dielectric thin film of the present invention has a high dielectric constant is that, surprisingly, the crystal axes of the lead titanium zirconate crystals are oriented in a certain direction, and the lead titanium zirconate thin film has a high dielectric constant. This is because forming multiple layers repairs thin film defects such as pinholes, and at the same time prevents electrical conduction through grain boundaries.

The present invention provides a lead titanium zirconate dielectric thin film having excellent electrical properties and a thickness that has conventionally been considered difficult to manufacture, and a method for manufacturing the same, and has extremely great industrial significance.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

However, the scope of the present invention is not limited in any way by the following examples.

Example 1 Preparation of lead titanium zirconate precursor solution: lead oxide F p
bo and zirconium acetylacetonate: zr ・(
CI13 GOCIICOC1+3) 4 and tetrabutoxydicune:Ti ・ (OC411g)
4 and PbTiO3/PbZr0. Molar ratio is 451
55, and heated and reacted in acetylacetone at a temperature of 100 to 110°C to prepare a lead titanium zirconate precursor solution with a concentration of 12.5% by weight in terms of composite metal oxide. .

After drying up the solvent by heating the prepared precursor solution, it was thermally decomposed at a temperature of 500°C to obtain a yellow powder. As a result of performing X-ray diffraction on the obtained yellow powder, it was confirmed that it was a crystal of lead titanium zirconate. The X-ray diffraction pattern of the obtained yellow powder is shown in FIG.

Production of lead titanium zirconate dielectric thin film: A glass substrate coated with a tin-doped indium oxide transparent conductive film (ITO) is immersed in the prepared lead titanium zirconate precursor solution maintained at 50 to 60°C. 47cm/min
A coating film of lead titanium zirconate precursor was formed by pulling at a speed of . Next, it was heated and fired in an electric furnace heated to a temperature of 500°C for 30 minutes. This dipping and heating and baking were repeated to obtain a transparent thin film body.

As a result of performing X-ray diffraction on the obtained thin film body, it was confirmed that it was a thin film body of lead titanium zirconate.

Dipping of the obtained lead titanium zirconate thin film
Table 1 shows the number of repetitions of heating and firing and the electrical properties. Moreover, the X-ray diffraction pattern of the obtained lead titanium zirconate thin film body is shown in FIG.

Example 2 Synthesis of lead-containing composite organometallic compound: Lead propionate: Pb (# in OCOC21) 2 and tetrabutoxyzirconium: Zr (OC4119)
) 4 and tetrabutoxytitanium: Ti (OC411
9) 4 was weighed out so that the PbTiO3/PbTioi molar ratio was 50150, and 13
The reaction was carried out by heating to a temperature of 0 to 140°C. Low-boiling substances were distilled off under reduced pressure to obtain a powdery reaction product. 1. From the R analysis, the elemental analysis of Pb, Ti + Zr, and the distilled amounts of butanol and butyl acetate, the average composition of the obtained reaction product is Pb-'h, ; Zr, ;
02 (OC4+19)t, ((OCOC2I
I(). I admitted that it was 6.

The resulting reaction product powder was thermally decomposed at a temperature of 600° C., and the resulting powder was subjected to X-ray diffraction, which confirmed that it was lead titanium zirconate.

Production of lead titanium zirconate dielectric thin film: The lead-containing composite organometallic compound powder obtained above was dissolved in acetylacetone, and a lead titanium zirconate forming precursor solution having a concentration of 12.5% by weight in terms of composite oxide was cleaved. .

After applying the precursor by dipping a glass substrate coated with an ITO film under the same conditions as in the example, the cleaved lead titanium zirconate forming precursor solution heated and maintained at a temperature of 50 to 60 ° C. , 30 to a temperature of 500℃
After heating and baking, dipping and heating were repeated four times to obtain a 5-layer laminated thin film body.The electrical properties of the obtained laminated thin film body were as follows.

Film thickness: d 6,000 people Capacitance: C0,
71μF/cd Specific dielectric constant: ε 480 Dielectric loss: tan δ 0.054 Specific resistance: 4X10
Comparative Example 1 A glass substrate coated with TTOIIQ was dipped in the lead titanium zirconate formation precursor solution prepared in Example 1 under the same conditions as in Example 1, and heated and baked to form a single-layer thin film of lead titanium zirconate. I got a body.

The electrical properties of the obtained thin film could not be measured due to conductivity.

[Brief explanation of the drawings] Figure 1 X-ray diffraction diagram of lead titanium zirconate powder obtained in Example 1 Figure 2 X-ray diffraction diagram of lead titanium zirconate thin film obtained in Example 1 Patent application Person Nippon Soda Co., Ltd. Agent Haruyuki Ito Yoshimi Yokoyama Figure 1 IQ'30' 50°
70° 90° Figure 2

Claims (1)

[Claims] 1 Composition formula % Formula % (1)) Method for producing a lead titanium zirconate dielectric thin film according to claim 4 11 Heating and firing temperature of a heat-resistant substrate coated with a precursor solution The method for producing a lead titanium zirconate dielectric thin film according to claim 4, wherein the temperature is 450 to 800°C, preferably 500 to 700°C.