JP3099567B2 - Method for producing lead zirconate titanate thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a lead zirconate titanate thin film, and more particularly to a method for producing lead zirconate titanate useful as a material for electronic parts.

[0002]

2. Description of the Related Art Lead zirconate titanate has excellent properties as a ferroelectric material, a piezoelectric material or a pyroelectric material, and has been widely applied to porcelain capacitors, actuators, pyroelectric infrared sensors and the like. . In general, when applied to these applications, lead zirconate titanate is used in bulk form, but with the miniaturization and high performance of electronic equipment, lead zirconate titanate must be used as a thin film. Have been tried, and as a method of forming a thin film, for example, a sputtering method (Japanese Patent Publication No. 63-238799), C
VD, MOCVD method (Proceedings of the 1991 Annual Meeting of the Ceramic Society of Japan, p. 427;
1), vacuum deposition method (Japanese Patent Application Laid-Open No. Hei 1-6306), coating and baking method (Japanese Patent Application Laid-Open No. Hei 3-283585), sol-gel method (Japanese Patent Application Laid-Open No. Hei 1-260870), and hydrothermal method (the eighth ferroelectric method). Proceedings of the Lectures on Body Application Conference, pp. 88-89) have been proposed.

[0003]

However, vapor phase methods such as sputtering, CVD, MOCVD, and vacuum evaporation require complicated and expensive equipment and expose the substrate to the flow of the source gas. For this reason, there is a problem that a film cannot be formed on a complicated base material or the back side of the substrate. The coating and baking method has a problem that it is necessary to repeat coating and baking, the operation is complicated, and it cannot be applied to a substrate having a complicated shape. The sol-gel method has a problem that microcracks are inevitably generated at the time of firing, and when the surface of the substrate has a step or the like, the film thickness may be uneven. The hydrothermal method has a problem in that the base material itself must be formed of metal Ti or a metal Ti film must be formed on the surface of the base material in advance, so that the development of the application is significantly lacking.

Accordingly, an object of the present invention is to make it possible to produce large-area lead zirconate titanate at a low cost without much restriction on the shape and material of the base material.

[0005]

According to the present invention, as a means for solving the above problems, basically, a composite alkoxide is produced by a liquid phase reaction of a lead carboxylate with a titanium alkoxide and a zirconium alkoxide. After preparing an aqueous solution of the composite alkoxide, the substrate surface is immersed in the aqueous solution to hydrolyze the composite alkoxide. Alternatively, the formed composite alkoxide may be denatured with ethanolamine, and the substrate may be immersed in the solution to hydrolyze.

[0006] Lead carboxylate includes 10 or less carbon atoms,
Preferably, those having 6 or less are suitable, and examples thereof include lead acetate, lead propionate, lead butyrate, lead caproate, and lead caprylate. This lead carboxylate may be directly added to an alkoxide solution containing titanium alkoxide and zirconium alkoxide described below, or may be dissolved in the same solvent as that used to dissolve the titanium alkoxide to form a solution, and the solution may be added. May be mixed with the alkoxide solution.

As the titanium alkoxide and the zirconium alkoxide, any one can be used, but an alkoxy group having 15 or less, preferably 8 or less carbon atoms is desirable. Typical examples are titanium alkoxide, titanium ethoxide, titanium isobutoxide (Ti (OC ₄ H ₉ ) ₄ ), titanium isopropoxide (Ti (OC ₃ H ₇ ) ₄ ), dibutoxide Ditriethanol-aminate titanium, dibutoxy-di (2- (hydroxyethylamino) ethoxy) titanium (Ti (C ₄ H ₉
O) _2. [N (C ₂ H ₄ OH) _2. (C ₂ H ₄ O) ₂ ]), but is not limited thereto.

As a solvent for performing the liquid phase reaction, ethylene glycol monoalkyl ether (ROCH ₂ CH ₂ O)
H) is preferably used. The ethylene glycol monoalkyl ether includes ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono n-propyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono n-butyl ether, ethylene glycol phenyl Ethers and the like are included, and commercially available trade names include methyl cellosolve, ethyl cellosolve and the like.

[0009]

When a lead carboxylate is reacted with a titanium alkoxide and a zirconium alkoxide in an ethylene glycol monoalkyl ether solution having an alcoholic hydroxyl group and an ether bond, a complex alkoxide is formed.
This complex alkoxide is dissolved in water to prepare an aqueous solution,
When the substrate is immersed in this and is gradually hydrolyzed, a nucleus of a film having a desired composition is formed on the surface of the substrate due to heterogeneous nucleation, and the nucleus grows as the hydrolysis proceeds, and the film and Become. By heat treating this film, a lead zirconate titanate thin film is formed.

[0010]

EXAMPLE 1 0.1 mol of lead acetate was dissolved in 0.8 mol of ethylene glycol monomethyl ether, heated and maintained at about 110 ° C. to completely evaporate water, and then cooled to about 50 ° C. , To which are added tetraisopropyl titanate and tetraisopropyl zirconate in the proportions shown in Table 1,
The reaction was performed at about 100 ° C. to obtain a composite alkoxide. This complex alkoxide was dissolved in 30 ml of ion-exchange distilled water at the concentration and temperature shown in Table 1, and the surface thereof was mirror-polished.
An alumina sintered body substrate having a size of 0 × 15 × 2 mm was immersed for 4 days. Thereafter, each substrate was heated to the temperature shown in Table 1, held for 1 hour, and then subjected to a heat treatment of cooling to room temperature. As a result, a lead zirconate titanate thin film was formed on the surfaces of the substrates other than Sample Nos. 1 and 2. Was.

[0011]

[Table 1] No. Pb (II) Ti (IV) Zr (IV) Pb: Ti: Zr Liquid temperature Heat treatment temperature (mM / l) (mM / l) (mM / l) (molar ratio) (° C) (° C) * 1 0.005 0.0025 0.0025 1: 0.5: 0.5 110 500 * 2 100 10 90 1: 0.1: 0.9 115 500 3 0.01 0.048 0.052 1: 0.48: 0.52 110 400 4 0.1 0.05 0.095 1: 0.05: 0.95 100 500 5 1 0.7 0.3 1: 0.7 : 0.3 40 700 6 10 5 5 1: 0.5: 0.5 5 800 7 100 40 60 1: 0.4: 0.6 0 900

The thin film X obtained for the sample No. 5 obtained
The line diffraction chart is shown in FIG. As is clear from the results in FIG. 1, according to the method of the present invention, a lead zirconate titanate thin film consisting of only a single perovskite phase can be obtained.

When the concentration of lead ions or the total concentration of titanium ions and zirconium ions contained in the immersion liquid is less than 0.01 mol as in sample No. 1, lead zirconate titanate is discretely precipitated in the form of islands. , Does not form a film,
When the concentration of lead ions or the total concentration of titanium ions and zirconium ions exceeds 100 mM as in Sample No. 2, heterogeneous nucleation using the substrate surface does not occur, and precipitates are precipitated in the aqueous solution by uniform nucleation. No film is obtained. Accordingly, the lead ion concentration and the total concentration of titanium ion and zirconium ion are 0.01 to 100, respectively.
Preferably, it is mM.

If the temperature of the immersion liquid is lower than 0 ° C., the deposition rate is extremely reduced and the film cannot be formed. If the temperature exceeds 110 ° C., bubbles are generated and the continuity, smoothness and homogeneity of the film are generated. Therefore, the liquid temperature is preferably 0 to 110 ° C. Further, when the heat treatment temperature is lower than 400 ° C., an amorphous phase or a pyrochlore phase is generated, and a ferroelectric thin film cannot be obtained.
If the temperature exceeds 00 ° C., the smoothness and homogeneity of the film are impaired, so that the heat treatment temperature is preferably in the range of 400 to 900 ° C.

[0015]

As described above, according to the present invention, a composite alkoxide of lead, titanium and zirconium is produced, and then hydrolyzed to deposit a thin film on the surface of the substrate immersed in the liquid. Heat-treating this to form a lead zirconate titanate thin film enables a uniform thin film to be manufactured without being affected by the material and shape of the substrate. As in the dry method described above, there is obtained an excellent effect that a large-area thin film having a desired composition without a loss due to evaporation of lead during sintering and having a desired molar ratio can be easily and inexpensively produced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an X-ray diffraction chart of a lead zirconate titanate thin film produced by the method of the present invention.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 25/00 H01L 41/24 CA (STN)

Claims (3)

(57) [Claims] 1. A composite alkoxide is produced by a liquid phase reaction of a lead carboxylate with a titanium alkoxide and a zirconium alkoxide, and an aqueous solution of the composite alkoxide is prepared. A method for producing a lead zirconate titanate thin film, comprising hydrolyzing. 2. The ion concentrations of lead, titanium and zirconium contained in the aqueous solution are Pb (II) and Ti (I
V) and Zr (IV) ion, 0.01 mM / l ≦ Pb
(II) ≦ 100 mM / l, 0.01 mM / l ≦ Ti (IV) ≦ 100
2. The method according to claim 1, wherein the value is in the range of mM / l, 0.01 mM / l≤Zr (IV) ≤100 mM / l. 3. The method according to claim 1, wherein the liquid phase reaction for producing the complex alkoxide is performed in a solution using ethylene glycol monoalkyl ether as a solvent.