TWI574281B - A ferroelectric film, a film forming method, and a method for manufacturing a ferroelectric film - Google Patents

Description

Strong dielectric film, film forming method and method for manufacturing ferroelectric film

The present invention relates to a ferroelectric film, a film forming method, and a method of manufacturing a ferroelectric film.

A method for producing a conventional Pb(Zr,Ti)O ₃ (hereinafter referred to as "PZT") film will be described.

A Pt film oriented, for example, at (111) is formed on a 4 inch wafer onto which the PZT sol gel solution is spin coated by a spin coater. Next, the coated PZT sol gel solution is heated and held on a hot plate to be dried, and after removing moisture, it is further heated and held on a hot plate maintained at a high temperature to perform pre-baking. This is repeated a plurality of times to form PZT amorphous.

Next, the PZT amorphous material which was subjected to the pre-baking was subjected to annealing treatment using a pressure lamp annealing apparatus (RTA: rapid thermal anneal) to carry out PZT crystallization. This crystallized PZT film system is composed of a perovskite structure. (For example, refer to Patent Document 1)

On the other hand, PZT has a Tc of 300 ° C or more, and although it has good ferroelectricity and piezoelectricity, it has become a problem in achieving lead-free system in the whole industry.

[prior technical literature] [Patent Document]

[Patent Document 1]: WO2006/087777

As described above, in the industry, the manufacture of a ferroelectric film composed of a non-lead material is required.

One aspect of the present invention is to produce a ferroelectric film composed of a non-lead material.

The following (1) to (22) are for explaining a plurality of aspects of the present invention.

(1) A ferroelectric film characterized by having K, Na, Nb, and O.

(2) The ferroelectric film according to (1) above, wherein the ferroelectric film is a (K _1-X Na _X )NbO ₃ film composed of a perovskite structure, and X satisfies the following formula: 0.3≦X≦0.7.

(3) The ferroelectric film according to (1) or (2) above, wherein the ferroelectric film is formed by a sol-gel method.

(4) The ferroelectric film according to any one of (1) to (3) above, comprising a crystalline oxide formed on at least one of the above and below the ferroelectric film.

(5) The ferroelectric film according to (4) above, wherein The aforementioned crystalline oxide has a perovskite structure.

(6) The ferroelectric film according to (4) or (5) above, wherein the crystalline oxide has a higher dielectric constant than the ferroelectric film.

The high dielectric constant referred to herein means that the dielectric constant of the entire crystalline oxide is higher than the dielectric constant of the entire ferroelectric film, and means the so-called substantial dielectric constant.

(7) The ferroelectric film according to any one of (4) to (6) above, wherein the crystalline oxide is formed in an island shape or a film shape.

(8) The ferroelectric film according to any one of (4) to (7) above, wherein the crystalline oxide has a thickness of 1 to 30 nm.

The thickness of the crystalline oxide referred to herein means the thickness of the crystalline oxide when it is formed only on one of the upper and lower of the ferroelectric film; when the crystalline oxide is formed on the ferroelectric film The upper and lower limits mean the total thickness of the two.

(9) The ferroelectric film according to any one of (4) to (8) above, wherein the crystalline oxide is Pb(Zr,Ti)O ₃ , and the total mass of Pb in the crystalline oxide The total mass of the ferroelectric film and the crystalline oxide is 1000 ppm or less.

(10) A film forming method characterized in that a sol-gel solution containing K, Na, and Nb is applied to a substrate by spin coating, as described above A coating film is formed on the substrate, and the coating film is pre-fired to form a ferroelectric material film on the substrate.

(11) The film forming method according to (10) above, wherein the total concentration of the K, Na, and Nb contained in the sol-gel solution is 10 to 50 mol/liter.

(12) The film forming method according to (10) or (11) above, wherein, when the ferroelectric material film is formed on the substrate, the formation of the coating film and the pre-baking are repeated a plurality of times. A ferroelectric material film composed of a plurality of coating films is formed on the substrate.

(13) A method for producing a ferroelectric film, which comprises forming a film of a ferroelectric material on a substrate by using the film forming method according to any one of (10) to (12) above, The ferroelectric material is heat-treated to form a ferroelectric material film, and a ferroelectric film in which the ferroelectric material film is crystallized is formed on the substrate.

(14) The method for producing a ferroelectric film according to (13) above, wherein the heat treatment is performed in a pressure range of 0.0993 to 0.98307 MPa.

(15) The method of producing a ferroelectric film according to the above (13) or (14), wherein the ferroelectric film is a ferroelectric film according to any one of the above (1) to (3).

(16) A method for producing a ferroelectric film, characterized in that a sol-gel solution containing K, Na, and Nb is coated on a substrate by a spin coating method. a liquid for forming a coating film on the substrate, and pre-sintering the coating film to form a ferroelectric material film on the substrate, and forming an island or film on the ferroelectric material film The first crystalline oxide or the first crystalline oxide forming material film is formed by heat-treating the ferroelectric material film and the first crystalline oxide forming material film in an oxygen atmosphere to form the ferroelectric A bulk dielectric film and a ferroelectric film in which the first crystalline oxide forming material film is crystallized.

(17) The method for producing a ferroelectric film according to the above (16), wherein before the coating film is formed on the substrate, an island-shaped or film-shaped second crystalline oxide or a second layer is formed on the substrate in advance. The material film for forming a crystalline oxide is formed on the second crystalline oxide or the second crystalline oxide-forming material film.

(18) A method for producing a ferroelectric film, characterized in that an island-shaped or film-shaped first crystalline oxide or a first crystalline oxide-forming material film is formed on a substrate by spin coating Applying a sol-gel solution containing K, Na, and Nb to the first crystalline oxide or the first crystalline oxide-forming material film to form the first crystalline oxide or the first A coating film is formed on the film for forming a crystalline oxide, and the coating film is pre-fired to form a strong dielectric layer on the first crystalline oxide or the first crystalline oxide forming material film. Electroplastic material film, Forming a masking film on the ferroelectric material film, and heat-treating the ferroelectric material film and the first crystalline oxide forming material film in an oxygen atmosphere, and suppressing K and Na by the mask film by the strong The dielectric material film is detached to form a ferroelectric film in which the ferroelectric material film and the first crystalline oxide forming material film are crystallized.

(19) The method for producing a ferroelectric film according to any one of the above (16), wherein the total concentration of the K, Na, and Nb contained in the sol-gel solution is 10 to 50 mol/liter. .

(20) The method for producing a ferroelectric film according to any one of the above (16) to (19) wherein, in forming the ferroelectric material film, the formation of the coating film and the pre-pretreatment are repeated After firing a plurality of times, a film of a ferroelectric material composed of a plurality of coating films is formed.

The method for producing a ferroelectric film according to any one of the above (16), wherein the heat treatment is performed in a pressure range of 0.0993 to 0.98307 MPa.

The method for producing a ferroelectric film according to any one of the above (16) to (21), wherein the ferroelectric film is as described in any one of the above (1) to (3) Electric film.

According to an aspect of the present invention, a ferroelectric film composed of a non-lead material can be manufactured.

Hereinafter, embodiments of the present invention will be described in detail using the drawings. The present invention is not limited by the following description, and it is obvious that those skilled in the art can make various changes in the form and details without departing from the scope of the invention. Therefore, the present invention is not limited to the description of the embodiments shown below.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing a ferroelectric film of an aspect of the present invention.

The ferroelectric film of the present embodiment has K, Na, Nb, and O, and is specifically a (K _1-X Na _X )NbO ₃ film 12.

Further, the above (K _1-X Na _X )NbO ₃ is composed of a perovskite structure.

The above X preferably satisfies the following formula (1).

(1) 0.3≦X≦0.7

The crystalline oxides 11 and 13 are formed on at least one of the above and below the (K _1-X Na _X )NbO ₃ film 12.

The crystalline oxides 11 and 13 are preferably a ferroelectric film composed of a perovskite-structured ferroelectric material represented by ABO ₃ , and the perovskite-structured ferroelectric material may be, for example, Pb ^{2+ .} A ferroelectric material of Pb(Zr,Ti)O _{3 having} a Z-position ion and containing Zr ⁴⁺ and Ti ⁴⁺ as a B-site ion. In this case, since the crystalline oxides 11 and 13 contain Pb, the total mass of the (K _1-X Na _X )NbO ₃ film 12 and the crystalline oxides 11 and 13 is in the crystalline oxides 11 and 13. The total mass of Pb is preferably 1000 ppm. Thereby, it becomes a lead content which can be called the lead-free degree.

Next, a method of manufacturing the ferroelectric film of the present embodiment will be described in detail with reference to Fig. 1 . This ferroelectric film is composed of a perovskite structure ferroelectric material represented by (K _1-X Na _X )NbO ₃ , and X satisfies the above formula (1).

(substrate)

For example, a base film oriented to a specified crystal face is formed on a substrate such as a 6 inch Si wafer. This base film uses, for example, a (111) oriented Pt film or an Ir film.

Next, a crystalline oxide 11 is formed on the base film. The crystalline oxide 11 may be an island-shaped or film-like crystalline oxide, or may be a well-known sol-gel solution for forming a crystalline oxide by a spin coating method to form a substrate. A coating film is formed on the film, and the coating film is pre-fired to form a film for forming a crystalline oxide film formed of the coating film on the base film. In addition, the formation of the coating film and the pre-baking may be repeated to form a film of a material for forming a crystalline oxide composed of a plurality of coating films.

Next, a sol-gel solution for forming the (K _1-X Na _X )NbO ₃ film 12 is prepared. The sol-gel solution contains: a raw material solution containing a hetero-acid containing K, Na and Nb; a polar solvent; and an unsaturated fatty acid. The total concentration of K, Na and Nb contained in the sol-gel solution may be 10 to 50 mol/liter.

The sol-gel solution is composed of a heteropolyacid ion having a Keggin-type structure in which a molecular structure is non-centrosymmetric and exhibits a non-linear shape, and the polyatomic acid ion containing the polyatomic acid ion has at least one defect, or The polyatomic acid ion of one of the heteropolyacid ions is replaced by another atom as a part of the precursor structure of the ferroelectric ceramic.

The above heteropolyacid ion has the general formula: [XM _y M ' _12-y O ₄₀ ] ^n- (wherein X is a hetero atom; M is a poly atom; M ' is a poly atom different from M; n is a valence; y = 1 to 11. The Keggin-type constructor is represented, and contains the above-mentioned heteropolyacid ion as a part of the ferroelectric ceramic precursor structure.

Further, the heteropoly acid ion may have a Keggin type structure represented by a general formula: [XM ₁₁ O ₃₉ ] ^n- (wherein X is a hetero atom; M is a poly atom; n is a valence), and The above-mentioned heteropolyacid ions are included as part of the precursor structure of the ferroelectric ceramic.

Further, the heteropolyacid ion has the following general formula: [XM _z M ' _11-z O ₃₉ ] ^n- (wherein, X is a hetero atom; M is a poly atom; M ' is different from M The atom; n is a valence; z = 1 to 10) represents a Keggin-type constructor, and contains the above-mentioned heteropolyacid ion as a part of the ferroelectric ceramic precursor structure.

Among the above heteropolymer acid ions, a hetero atom may be composed of a group of B, Si, P, S, Ge, As, Mn, Fe, and Co, and the polyatoms may be composed of Mo, V, W, Ti, and Al. Nb and Ta are formed in groups, and the above-mentioned heteropoly acid ions are included as part of the ferroelectric ceramic precursor structure.

The polar solvents are methyl ethyl ketone, 1,4-dioxane, 1,2-dimethoxyethane acetamide, N -methyl-2-pyrrolidone, acetonitrile, dichloromethane, nitromethane, three Any one or a combination of methyl chloride, dimethylformamide, and monomethylformamide.

The unsaturated fatty acid is any one or a combination of a monounsaturated fatty acid, a di-unsaturated fatty acid, a tri-unsaturated fatty acid, a tetra-unsaturated fatty acid, a penta-unsaturated fatty acid, and a hexa-unsaturated fatty acid.

Examples of the monounsaturated fatty acid include crotonic acid, myristic acid, palmitoleic acid, oleic acid, elaidic acid, trans 11-octadecenoic acid, cis-9-eicosenoic acid, eicosenoic acid, and cis. 13-docosaenoic acid, cis-15-tetracosenoic acid, any one or a combination of these may be used.

The diunsaturated fatty acid may, for example, be linoleic acid, eicosadienoic acid or docosadienoic acid, and any one or a combination of these may be used.

Examples of the triunsaturated fatty acid include linoleic acid, (5Z, 9Z, 12Z) octadecatrienoic acid, tung acid, (5Z, 8Z, 11Z) eicosatrienoic acid, dihomo-γ-linolenic oil. As the acid (DGLA) or eicosatrienoic acid, any one or a combination of these may be used.

Examples of the tetra-unsaturated fatty acid include (6Z, 9Z, 12Z, 15Z) octadecaenoic acid, (5Z, 8Z, 11Z, 14Z) eicosatetraenoic acid (arachidonic acid), eicosatetraene. As the acid, (7Z, 10Z, 13Z, 16Z) docosatetraenoic acid, any one or a combination of these may be used.

Examples of the penta-unsaturated fatty acid include (5Z, 8Z, 10E, 12E, 14Z) eicosapentaenoic acid, (5Z, 8Z, 11Z, 14Z, 17Z) eicosapentaenoic acid, (4Z, 7Z, 10Z, 13Z, 16Z) eicosapentaenoic acid, docosapentaenoic acid (linoleic acid, DPA), docosapentaenoic acid, any of these or A combination of plurals.

The hexa-unsaturated fatty acid may, for example, be docosahexaenoic acid (DHA) or docosahexaenoic acid (decanoic acid), and any one or a combination of these may be used.

Next, the above sol-gel solution is applied onto the crystalline oxide 11. The contact angle of the sol-gel solution with the substrate was measured and found to be 20 or less. Further, the contact angle with the substrate may be 1 to 40 (preferably 1 to 20).

The coating of the sol-gel solution was carried out by a spin coating method. Thereby, a coating film is formed on the crystalline oxide 11, and the coating film is pre-fired at a temperature of 25 to 450 ° C (preferably at a temperature of 450 ° C), whereby the crystalline oxide 11 is used. A film of (K _1-X Na _X )NbO ₃ material composed of a coating film was formed into a film. Further, the (K _1-X Na _X )NbO ₃ material film composed of a plurality of coating films may be formed on the crystalline oxide 11 by repeating the formation and pre-baking of the coating film a plurality of times. Film formation.

Next, the crystalline oxide 13 is formed on the (K _1-X Na _X )NbO ₃ material film. As the crystalline oxide 13, the same as the crystalline oxide 11 can be used.

(crystallization method)

By heat-treating the crystalline oxide 11, the (K _1-X Na _X )NbO ₃ material film, and the crystalline oxide 13 in an oxygen atmosphere at a temperature of 450 to 900 ° C (preferably at a temperature of 900 ° C), These are crystallized. The heat treatment conditions at this time may be carried out in a pressure range of 0.0993 to 0.98307 MPa. Moreover, the heat treatment conditions at this time may be baked for 1 to 5 minutes in a pressurized oxygen atmosphere at a temperature increase rate of 2 to 9.9 atm and 100 to 150 ° C/sec. Further, when the (K _1-X Na _X )NbO ₃ material film is concentrated and crystallized, the film thickness of the (K _1-X Na _X )NbO ₃ material film is preferably 300 nm or more.

The (K _1-X Na _X )NbO ₃ film 12 crystallized in this manner preferably has X satisfying the following formula (1).

(1) 0.3≦X≦0.7

The (K _1-X Na _X )NbO ₃ film 12 has almost no bubbles even in a film having a thickness of 500 nm or more. In other words, by forming a film in this manner, a film having a good thickness can be formed. The reason for this is that the organic component is formed in a structure in which the organic component disappears in the film thickness direction, and it hardly shrinks in the surface of the substrate, and is offset by the expansion due to oxidation. Therefore, the substrate has almost no warpage.

Further, by repeating the film formation and crystallization of the above-mentioned (K _1-X Na _X )NbO ₃ material film, the (K _1-X Na _X )NbO ₃ film 12 having a film thickness of 2 μm or more can be formed.

Further, the total thickness of the crystalline oxides 11 and 13 crystallized in the above manner is 1 to 30 nm, preferably 15 to 25 nm, and more preferably 20 nm.

Further, in FIG. 1, although the crystalline oxides 11 and 13 are formed on both the upper and lower sides of the ferroelectric film 12, they may be formed on at least one of the upper and lower portions of the ferroelectric film 12. Crystalline oxide. Thus, when the crystalline oxide is formed only on one of the upper and lower of the ferroelectric film, the crystallization of one of them The thickness of the oxide is 1 to 30 nm, preferably 15 to 25 nm, more preferably 20 nm.

The crystals in the crystalline oxides 11 and 13 are nucleus when the (K _1-X Na _X )NbO ₃ material film is crystallized, so that it is difficult to crystallize into a perovskite structure (K _1-X Na Crystallization of the _X ) NbO ₃ material film proceeds rapidly. Since the crystalline oxides 11 and 13 act as a nucleus of crystallization, it is sufficient that at least one of the (K _1-X Na _X )NbO ₃ material films is formed with a crystalline oxide.

When the crystalline oxide 11 is formed only under the (K1 _{- X} Na _X )NbO ₃ material film, a masking film may be formed on the (K _1-X Na _X )NbO ₃ material film in advance. The masking film is used to suppress the detachment of K and Na from the (K _1-X Na _X )NbO ₃ material film by crystallizing the (K _1-X Na _X )NbO ₃ material film by heat treatment in an oxygen atmosphere. The function of the person can use a variety of people.

Further, the crystalline oxides 11 and 13 preferably have a higher dielectric constant than the (K _1-X Na _X )NbO ₃ film 12 of the ferroelectric film. The high dielectric constant as used herein means that the dielectric constant of the entire crystalline oxides 11 and 13 is higher than the dielectric constant of the entire ferroelectric film 12, that is, the so-called substantial dielectric constant. Thereby, when a voltage is applied in series to the crystalline oxides 11 and 13 and the (K _1-X Na _X )NbO ₃ film 12, the (K _1-X Na _X )NbO ₃ film 12 having a low dielectric constant is applied. electric field.

According to this embodiment, the (K _1-X Na _X )NbO ₃ film 12 of a ferroelectric film made of a non-lead material can be produced.

Further, according to the present embodiment, the (K _1-X Na _X )NbO ₃ material film is heat-treated by being crystallized in a state of being sandwiched between the crystalline oxide 11 and the crystalline oxide 13, so that it can be suppressed (K). The K in the _1-X Na _X )NbO ₃ material film is desorbed from Na, and the film quality of the crystallized (K _1-X Na _X )NbO ₃ film 12 is improved.

Further, at the time of by _{(K 1-X Na X)} NbO 3 film material crystallized when treated with heat in a pressurized oxygen atmosphere, can be suppressed _{(K 1-X Na X)} NbO 3 material film of Na and K The film quality of the crystallized (K _1-X Na _X )NbO ₃ film 12 is improved by detachment.

Further, the crystalline oxides 11 and 13 may be removed after crystallization of the (K _1-X Na _X )NbO ₃ material film. The removal method at this time is, for example, an etching method.

[Examples]

A 10 to 30 nm Ti film was formed by sputtering on a 6-inch Si wafer through a ruthenium oxide film. In detail, it is formed by an RF sputtering method. The Ti film plays the role of a close layer of platinum and ruthenium oxide. The film formation conditions of the Ti film were formed by a power supply output of an argon gas pressure of 0.2 Pa and 0.12 kW, and a film formation time of 20 minutes. The substrate temperature was carried out at 200 °C.

Next, the Ti film was subjected to heat treatment at 650 ° C for 5 minutes by RTA (Rapid Thermal Anneal). In an oxygen atmosphere, it was carried out at 9.9 atm and 100 ° C / sec.

Next, a 100 nm first Pt film was formed on the Ti film by a sputtering method at a temperature of 550 to 650 °C. It was formed by a power supply output of 0.4 Pa of argon gas and 100 W of DC power, and a film formation time of 25 minutes.

Next, a second Pt film of 100 nm was formed by vapor deposition on the first Pt film. Film formation at room temperature.

It was formed by a power supply of 3.3 × 10 ^-3 Torr and 10 kV and formed at a film formation time of 4 minutes.

Next, the Si wafer is subjected to heat treatment at 650 to 750 ° C for 1 to 5 minutes by RTA. Thus, a 6-inch Si wafer having a (111) oriented Pt film formed on the surface was prepared.

Next, a PZT ferroelectric material film for forming a crystalline oxide is formed on the Si wafer. The film formation conditions at this time are as follows.

A sol-gel solution for forming a PZT ferroelectric thin film was prepared by using Mitsubishi Materials Co., Ltd., and a 15% concentration of a 10% by weight E1 solution was added to lead in a butanol solvent. The addition of dimethylaminoethanol to the basic alcohol in a ratio of E1 sol gel solution: dimethylaminoethanol = 7:3 in the commercially available sol-gel solution showed a strong pH=12. Alkaline. Using this solution, spin coating of a PZT film was carried out. The spin coater was produced using MS-A200 manufactured by Mikasa Co., Ltd. First, after rotating at 800 rpm for 5 seconds and 1500 rpm for 10 seconds, the rotation speed was gradually increased to 8000 rpm (6000 rpm or more), and after rotating for 1 minute, the heating plate was placed at 150 ° C (a ceramic heating plate made by As One Co., Ltd.). AHS-300) was placed in the atmosphere for 5 minutes, and then placed on a hot plate (with AHS-300) at 300 ° C for 5 minutes, and then placed in the atmosphere in the same manner, and then cooled to room temperature. Thus, a PZT thin film having a thickness of 10 nm containing 15% of excess lead was formed on the Si wafer.

Next, a sol-gel solution having a contact angle with the PZT thin film of 40 or less, preferably 20 or less is prepared. In detail, the sol gel solution The invention comprises: a raw material solution containing a heteropoly acid containing K, Na and Nb; a polar solvent; and an unsaturated fatty acid.

(K _1-X Na _X ) a raw material solution for forming a film of NbO _{3 , which} is formed by mixing with a heteropoly acid, and is a hetero atom inserted into a metal oxyacid skeleton (X ₁ M _m O _n ) ^x -type polybasic acid. . Polyatoms: M=Mo, V, W, Ti, Al, Nb, Ta; heteroatoms mean elements other than H and C; preferably M=B, Si, P, S, Ge, As, Fe A sol-gel solution for forming an oxide film composed of Co and Bi.

The polar solvents are methyl ethyl ketone, 1,4-dioxane, 1,2-dimethoxyethane acetamide, N -methyl-2-pyrrolidone, acetonitrile, dichloromethane, nitromethane, three Any one or a combination of methyl chloride, dimethylformamide, and monomethylformamide.

Examples of unsaturated fatty acids, monounsaturated fatty acids include crotonic acid, myristic acid, palmitoleic acid, oleic acid, elaidic acid, trans 11-octadecenoic acid, cis-9-eicosenoic acid, and 20 carbon. Oleic acid, cis 13-docosaenoic acid, cis 15-tetracosenoic acid; diunsaturated fatty acids may include linoleic acid, eicosadienoic acid, docosadienoic acid; Examples of saturated fatty acids include linoleic acid, (5Z, 9Z, 12Z) octadecatrienoic acid, tung acid, (5Z, 8Z, 11Z) eicosatrienoic acid, dihomo-γ-linolenic acid, and Decadienoic acid; tetraunsaturated fatty acid (6Z, 9Z, 12Z, 15Z) octadecaenoic acid, (5Z, 8Z, 11Z, 14Z) eicosatetraenoic acid, eicosatetraenoic acid , (7Z, 10Z, 13Z, 16Z) docosatetraenoic acid; penta-unsaturated fatty acid can be enumerated (5Z, 8Z, 10E, 12E, 14Z) eicosapentaenoic acid, (5Z, 8Z, 11Z, 14Z , 17Z) eicosapentaenoic acid, (4Z, 7Z, 10Z, 13Z, 16Z) - eicosapentaenoic acid, docosapentaenoic acid, and docosapentaenoic acid; hexa-hexaenoic acid can be exemplified by docosahexaenoic acid, Tetradecenoic acid.

Next, a coating film of the first layer was formed on the PZT thin film by coating the sol-gel solution on the PZT thin film by a spin coating method. Specifically, 500 μL of the sol-gel solution was applied, and the temperature was raised from 0 to 500 rpm in 3 seconds, held at 500 rpm for 3 seconds, and then rotated at 2000 rpm for 60 seconds, and then stopped.

Next, the coating film of the first layer was heated at a temperature of 200 ° C for 1 minute with a hot plate, and then calcined at a temperature of 450 ° C for 1 minute. Thereby, a first layer of a ferroelectric material amorphous film having a film thickness of 125 nm was formed on the first PZTN material film.

Next, a coating film of the second layer was formed on the first dielectric layer of the dielectric material film in the same manner as the coating film of the first layer. Next, the coating film of the second layer is heated in the same manner as the coating film of the first layer, and pre-baking is performed. Thereby, a second dielectric thin dielectric material film having a film thickness of 125 nm is formed on the first layer of the ferroelectric material film.

Next, a coating film of the third layer was formed on the second layer of the ferroelectric material film in the same manner as the coating film of the second layer. Next, the coating film of the third layer is heated in the same manner as the coating film of the first layer, and pre-baking is performed. Thereby, a third dielectric thin dielectric material film having a film thickness of 125 nm is formed on the second dielectric dielectric material film. This was repeated to form a 12-layer film of a strong dielectric material. As described above, a ferroelectric material film having a thickness of 1.5 μm composed of 12 layers can be formed into a film.

Next, a film of a PZT ferroelectric material film which forms a crystalline oxide is formed on the ferroelectric material film. The film formation conditions at this time are the same as those of the PZT film described above.

Next, the ferroelectric material film and the PZT film are subjected to heat treatment by pressurizing RTA, whereby the film is crystallized to form a (K _1-X Na _X )NbO ₃ film of a ferroelectric film, PZT. Crystallized film. In this case, the heat treatment conditions were carried out in an oxygen atmosphere pressurized at 9.9 atm by an oxygen partial pressure at a temperature increase rate of 100 ° C / sec, and the temperature was instantaneously raised to 900 ° C for 1 minute to carry out crystallization.

Further, in the present embodiment, a ferroelectric film of 1.5 μm is formed, but a ferroelectric film having a thick film thickness or a ferroelectric film having a small film thickness can be formed.

2 is a SEM photograph of a (K, Na) NbO ₃ film of a ferroelectric film (film thickness: 1.5 μm) of Sample 1.

Fig. 3 is a P-E hysteresis characteristic diagram showing the results of the hysteresis evaluation of the ferroelectric film of Sample 1.

As shown in FIG. 3, it was confirmed that the ferroelectric film of the sample 1 had excellent hysteresis characteristics. Further, the horizontal axis of Fig. 3 indicates the applied voltage (Volts), and the vertical axis of Fig. 3 indicates the residual polarization (μC/cm ² ).

11‧‧‧ Crystalline oxides

12‧‧‧(K _1-X Na _X )NbO ₃ film

13‧‧‧ Crystalline oxides

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing a ferroelectric film of an aspect of the present invention.

2 is a SEM photograph of a (K _1-X Na _X )NbO ₃ film.

Fig. 3 is a graph showing the results of performing the hysteresis evaluation of (K _1-X Na _X )NbO ₃ shown in Fig. 2.

11‧‧‧ Crystalline oxides

12‧‧‧(K _1-X Na _X )NbO ₃ film

13‧‧‧ Crystalline oxides

Claims (19)

A ferroelectric film characterized by having K, Na, Nb, and O, and the ferroelectric film is a (K _1-X Na _X )NbO ₃ film composed of a perovskite structure, and X satisfies Description: 0.3≦X≦0.7. The ferroelectric film of claim 1, wherein the ferroelectric film is formed by a sol-gel method. A ferroelectric film according to claim 1 or 2, comprising a crystalline oxide formed on at least one of the above and below the ferroelectric film. A ferroelectric film according to claim 3, wherein the crystalline oxide has a perovskite structure. A ferroelectric film according to claim 3 or 4, wherein the crystalline oxide has a higher dielectric constant than the ferroelectric film. The ferroelectric film according to claim 3 or 4, wherein the crystalline oxide is formed into an island shape or a film shape. A ferroelectric film according to claim 3 or 4, wherein the crystalline oxide has a thickness of 1 to 30 nm. The ferroelectric film according to claim 3 or 4, wherein the crystalline oxide is Pb(Zr,Ti)O ₃ , and the total mass of Pb in the crystalline oxide is relative to the above-mentioned ferroelectric The total mass of the bulk film and the crystalline oxide is 1000 ppm or less. A film forming method characterized in that a sol-gel solution containing K, Na, and Nb is applied onto a substrate by a spin coating method to form a coating film on the substrate, and the coating is performed by pre-baking. The film forms a ferroelectric material film on the substrate, and the total concentration of the K, Na, and Nb contained in the sol-gel solution is 10 to 50 mol/liter. The film forming method of claim 9, wherein when the ferroelectric material film is formed on the substrate, the formation of the coating film and the pre-baking are repeated a plurality of times to form a film on the substrate A film of a ferroelectric material composed of a plurality of coating films. A method for producing a ferroelectric film, characterized in that a film of a ferroelectric material is formed on a substrate by using a film forming method according to claim 9 or 10, wherein the ferroelectric material is heat-treated in an oxygen atmosphere The bulk material film is formed on the substrate by a ferroelectric film in which the ferroelectric material film is crystallized. The method for producing a ferroelectric film according to claim 11, wherein the heat treatment is performed in a pressure range of 0.0993 to 0.98307 MPa. The method for producing a ferroelectric film according to claim 11 or 12, wherein the ferroelectric film is a ferroelectric film of claim 1 or 2. A method for producing a ferroelectric film, characterized in that a sol-gel solution containing K, Na and Nb is applied onto a substrate by a spin coating method to form a coating film on the substrate by calcination Forming a coating film on the substrate to form a ferroelectric material film on the substrate, and forming an island-shaped or film-like first crystalline oxide or a first crystalline oxide on the ferroelectric material film In the material film, the ferroelectric material film and the first crystalline oxide forming material film are heat-treated in an oxygen atmosphere to form the ferroelectric material film and the first crystalline oxide forming material film. The crystallized ferroelectric film has a total concentration of K, Na, and Nb contained in the sol-gel solution of 10 to 50 mol/liter. The method for producing a ferroelectric film according to claim 14, wherein before the coating film is formed on the substrate, an island-shaped or film-shaped second crystalline oxide or second crystal is formed in advance on the substrate. The material film for forming an oxide is formed on the second crystalline oxide or the second crystalline oxide forming material film. A method for producing a ferroelectric film, characterized in that an island-shaped or film-shaped first crystalline oxide or a first crystalline oxide-forming material film is formed on a substrate, and the spin coating method is used for the The first crystalline oxide or the first crystalline oxide-forming material film is coated with K, Na, and Nb. In the sol-gel solution, a coating film is formed on the first crystalline oxide or the first crystalline oxide-forming material film, and the coating film is pre-fired to form the first crystallinity. Forming a ferroelectric material film on the oxide or the first crystalline oxide-forming material film, forming a mask film on the ferroelectric material film, and heat-treating the ferroelectric material film in an oxygen atmosphere; In the first crystalline oxide-forming material film, the shielding film suppresses K and Na from being separated from the ferroelectric material film, thereby forming the ferroelectric material film and the first crystalline oxide. In the ferroelectric film in which the material film is crystallized, the total concentration of the K, Na, and Nb contained in the sol-gel solution is 10 to 50 mol/liter. The method for producing a ferroelectric film according to any one of claims 14 to 16, wherein the forming of the ferroelectric material film is repeated by forming the coating film and the pre-firing into a plurality Next, a film of a ferroelectric material composed of a plurality of coating films is formed. The method for producing a ferroelectric film according to any one of claims 14 to 16, wherein the heat treatment is carried out in a pressure range of 0.0993 to 0.98307 MPa. A method of manufacturing a ferroelectric film according to any one of claims 14 to 16, wherein The above ferroelectric film is a ferroelectric film of the first or second aspect of the patent application.