JP5035568B2 - Ceramic film, manufacturing method thereof, semiconductor device, piezoelectric element and actuator - Google Patents

Description

The present invention relates to a ceramic film, a manufacturing method thereof , a semiconductor device , a piezoelectric element, and an actuator .

  At present, ferroelectric films having a layered perovskite structure (for example, BiLaTiO-based, BiTiO-based, SrBiTaO-based) have been proposed as ferroelectric films applied to semiconductor devices (for example, ferroelectric memories (FeRAM)). A ferroelectric film having a layered perovskite structure is generally formed by crystal growth from an amorphous state.

  By the way, when a ferroelectric film having a layered perovskite structure is formed by this forming method, the ferroelectric film has a crystal growth rate in the c-axis direction and a crystal growth rate in the a- and b-axis directions due to the crystal structure. Will be slower. That is, the crystal grows easily in the a and b axis directions. Therefore, according to the above formation method, the ferroelectric film having the layered perovskite structure has a rough surface morphology. That is, a gap (for example, a hole or a groove) is generated between crystals of the obtained ferroelectric film.

  An object of the present invention is to provide a method for producing a ceramic film, which can improve the surface morphology of the ceramic film.

  Another object of the present invention is to provide a ceramic film obtained by the method for producing a ceramic film of the present invention.

Another object of the present invention is to provide a semiconductor device , a piezoelectric element and an actuator to which the ceramic film of the present invention is applied.

(Ceramic film manufacturing method)
(A) The first method for producing a ceramic film of the present invention is as follows:
Including crystallizing the raw material body to form a ceramic film,
The raw material body includes a mixture of different types of raw materials,
Different types of raw materials have a relationship in which at least one of crystal growth conditions and crystal growth mechanism in crystallization of the raw materials is different from each other.

  Here, the different types of raw materials refer to a relationship between the raw materials in which at least one of the crystal growth conditions and the crystal growth mechanism is different from each other. That is, whether the types of raw materials are different is determined from the viewpoint of whether at least one of the crystal growth conditions and the crystal growth mechanism is different.

  Examples of crystal growth conditions and crystal growth mechanisms in crystallization of raw materials include crystallization temperature, crystal nucleus formation temperature, crystal growth temperature, crystal growth rate, crystal nucleus formation rate, crystal nucleus size, and crystallization method. Is included.

  In this invention, a raw material body contains the raw material from which a kind differs. That is, the raw material body includes two or more kinds of raw materials. Different types of raw materials have a relationship in which at least one of crystal growth conditions and crystal growth mechanism in crystallization of the raw materials is different from each other. For this reason, by controlling various conditions, for example, one raw material can be crystallized in advance of the other raw materials, and the other raw materials can be crystallized in the gap between crystals caused by the one raw material. . That is, a gap generated between crystals due to one raw material can be filled with crystals due to another raw material. Therefore, the surface morphology of the ceramic film can be improved.

  Further, by controlling various conditions, one raw material and another raw material can be crystallized simultaneously. For example, the crystallization temperature can be adjusted by replacing a part of the metal element of the raw material with another element. Since the crystallization temperature can be adjusted, the crystallization temperatures of different types of raw materials can be made substantially close to each other. If the crystallization temperatures of different types of raw materials can be made substantially similar, different types of raw materials can be crystallized simultaneously.

(B) The second method for producing a ceramic film of the present invention comprises:
Including crystallizing the raw material body to form a ceramic film,
The raw material body includes a mixture of different types of raw materials,
Different types of raw materials have different crystal structures of crystals obtained from the raw materials.

  Here, different types of raw materials refer to the relationship between the raw materials such that the crystal structures of the crystals obtained from the raw materials are different from each other. That is, whether or not the type of raw material is different is determined from the viewpoint of whether or not the crystal structure of the crystal obtained by the raw material is different.

The difference in the crystal structure of the crystal obtained from the raw material is, for example, that of m when the crystal obtained from the raw material is represented as (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- Differences are included.

  In the present invention, different types of raw materials are in such a relationship that the crystal structures of crystals resulting from the raw materials are different. If the crystal structure of the crystal obtained from the raw material is different, the crystal growth conditions and the crystal growth mechanism of the raw material are different. Therefore, the same operational effects as those of the first method for producing a ceramic film of the present invention can be achieved.

(C) The third method for producing a ceramic film of the present invention comprises:
Including crystallizing the raw material body to form a ceramic film,
The raw material body includes a mixture of different types of raw materials,
Different types of raw materials are crystallized independently of each other at least in the initial stage of crystallization.

  Here, different types of raw materials refer to the relationship between the raw materials that are crystallized independently of each other at least in the initial stage of crystallization.

  In the third method for producing a ceramic film of the present invention, different types of raw materials are crystallized independently of each other at least at the initial stage of crystallization. For this reason, crystals of other raw materials can be grown in the gaps between the crystals of one raw material. As a result, generation of gaps between crystals can be suppressed, and surface morphology is improved.

  The manufacturing method of the 1st-3rd ceramic film | membrane of this invention can take at least one of the following aspects.

  (A) The ceramic film is a ferroelectric material.

  (B) The ceramic film is a paraelectric material.

  (C) The ceramic film is an aspect in which a ferroelectric and a paraelectric are mixed.

(D) Among the relationships between the raw materials of different types, at least one binary relationship,
This is a mode in which the crystallization temperatures in the crystallization of the raw materials are different from each other.

(E) Among the relationships between raw materials of different types, at least one binary relationship,
This is a mode in which the formation temperatures of crystal nuclei in crystallization of raw materials are different from each other.

(F) In the relationship between at least one of the different types of raw materials,
This is a mode in which crystal growth temperatures in crystallization of raw materials are different from each other.

(G) Among at least one of the relationships between different types of raw materials,
This is a mode in which crystal growth rates in crystallization of raw materials are different from each other.

(H) Among the relationships between the raw materials of different types, in at least one binary relationship,
This is a mode in which the formation speed of crystal nuclei in crystallization of raw materials is different from each other.

(I) In the relationship between at least one of the different types of raw materials,
This is a mode in which the sizes of crystal nuclei in crystallization of the raw materials are different from each other.

(J) Among at least one of the relationships between the different types of raw materials,
The crystallization methods in the crystallization of the raw materials are different from each other.

  (K) It is an aspect in which different types of raw materials are crystallized with a time shift.

  (L) Different types of raw materials are forms in which the crystal nuclei in the crystallization of the raw materials are shifted in time.

  (M) It is an aspect in which raw materials of different types are crystallized at the same time.

  In addition, when different types of raw materials are crystallized at the same time, crystal growth caused by other raw materials is blocked. As a result, the obtained crystal can be microcrystallized. When the crystals are microcrystallized, the gaps between the crystals are narrowed and the surface morphology is improved.

  When different types of raw materials are crystallized at the same time, it is preferable to use raw materials having different crystal structures of the obtained ceramics. By making the crystal structures different, the crystal growth conditions and crystal growth mechanism in crystallization of the raw material can be changed simultaneously.

(N) Different types of raw materials have different m values when the ceramics obtained from the raw materials are represented as (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- It is an aspect.

  (O) The raw material body is formed on the substrate by the LSMCD method.

  When a raw material body is formed on a substrate by the LSMCD method, the raw material body is introduced onto the substrate in a mist form by ultrasonic waves. For this reason, the mixed state of different types of raw materials is improved. Therefore, according to this aspect, a ceramic film having fine crystals can be obtained.

  The raw material body may be formed on a substrate by separately supplying different types of raw materials.

  Alternatively, the raw material body may be formed on a substrate by simultaneously supplying different types of raw materials.

  (P) The raw material body is formed on the substrate by spin coating or dipping.

  (Q) The raw material is an embodiment that is at least one of a sol-gel raw material and a MOD raw material.

  (R) The raw material body includes an sol-gel raw material and a MOD raw material.

  Further, in the embodiments (p) and (q), the sol-gel raw material may be an embodiment in which polycondensation is performed by hydrolysis.

  In addition, the sol-gel raw material has a crystal structure that is the same as or similar to the crystal structure of the crystal when the raw material is crystallized. According to this aspect, crystallization of the sol-gel raw material can be facilitated.

  The MOD raw material may be a polynuclear complex raw material.

(S) The raw material body has different types of sol-gel raw materials,
Different types of sol-gel raw materials are different in the degree of polycondensation or the composition of metal elements.

(T) The raw material body has different types of sol-gel raw materials,
Different types of raw materials are not mixed at the atomic level.

  Here, “mixed at the atomic level” means, for example, that atoms constituting the raw material are mixed with each other. That is, the raw materials are preferably mixed in a state where a single molecule or aggregate is maintained. If the raw materials are not mixed at the atomic level, the effects of the present invention can be reliably achieved, and the characteristics of the ceramic film can be further improved.

(D) The fourth method for producing a ceramic film of the present invention comprises:
Including crystallizing the raw material body to form a ceramic film,
The raw material body is crystallized so that a plurality of phases are formed.

  The ceramic film can take one of the following modes.

  (A) The ceramic film is a ferroelectric material.

  (B) The ceramic film is a paraelectric material.

  (C) The ceramic film is an aspect in which a ferroelectric and a paraelectric are mixed.

(E) The fifth method for producing a ceramic film of the present invention comprises:
Including a step of forming a ceramic film by crystallizing a ceramic raw material liquid containing the first raw material liquid and the second raw material liquid,
The first raw material liquid and the second raw material liquid have a relationship of different types,
The first raw material liquid is a raw material liquid for producing a ferroelectric having a Bi-based layered perovskite structure,
The second raw material liquid is a raw material liquid for generating an ABO-based oxide whose A site is Bi.

  By forming a ceramic film from the ceramic raw material liquid of the present invention, for example, a ferroelectric film having predetermined characteristics can be formed at a low temperature. Moreover, the ceramic film obtained with the ceramic raw material liquid of the present invention is excellent in terms of surface morphology.

  The molar ratio of the ferroelectric generated based on the first raw material liquid and the ABO-based oxide generated based on the second raw material liquid is 100: 20 to 100: 100. preferable. As a result, a ferroelectric film having predetermined characteristics at a low temperature can be formed more reliably.

  The first raw material liquid is a solution in which a metal compound or a metal inorganic compound of a constituent metal element of the ferroelectric is dissolved in a solvent, and the second raw material liquid is a constituent metal element of the ABO-based oxide. The metal compound or metal inorganic compound can be dissolved in a solvent.

(F) The sixth method for producing a ceramic film of the present invention comprises:
Including a step of forming a ceramic film by crystallizing the ceramic raw material liquid containing the third raw material liquid and the fourth raw material liquid,
The third raw material liquid and the fourth raw material liquid are in a relationship of different types,
The third raw material liquid is a raw material liquid for generating a PZT ferroelectric.
The fourth raw material liquid is a raw material liquid for generating an ABO-based oxide whose A site is Pb.

  By forming the ceramic film with the ceramic raw material liquid of the present invention, for example, the same effects as the fifth ceramic film manufacturing method of the present invention can be achieved.

  The molar ratio of the ferroelectric generated based on the third raw material liquid and the ABO-based oxide generated based on the fourth raw material liquid is 100: 20 to 100: 100. preferable. Thereby, a ferroelectric film having predetermined characteristics at a low temperature can be formed more reliably.

  The third raw material liquid is a solution obtained by dissolving a metal compound or a metal inorganic compound of a constituent metal element of the ferroelectric in a solvent, and the fourth raw material liquid is a constituent metal element of the ABO-based oxide. The metal compound or metal inorganic compound can be dissolved in a solvent.

(G) A seventh method for producing a ceramic film of the present invention includes:
Including a step of forming a ceramic film by crystallizing a ceramic raw material liquid containing a fifth raw material liquid and a sixth raw material liquid,
The fifth raw material liquid is a raw material liquid for producing a ferroelectric having a Bi-based layered perovskite structure or a PZT-based ferroelectric,
The sixth raw material liquid is a raw material liquid for generating an ABO-based oxide whose B site is Ge.

  By forming the ceramic film with the ceramic raw material liquid of the present invention, for example, the same effects as the fifth ceramic film manufacturing method of the present invention can be achieved.

  The molar ratio of the ferroelectric generated based on the fifth raw material liquid and the ABO-based oxide generated based on the sixth raw material liquid may be 100: 20 to 100: 100. preferable. Thereby, a ferroelectric film having predetermined characteristics at a low temperature can be formed more reliably.

  The fifth raw material liquid is a solution in which a metal compound or a metal inorganic compound of a constituent metal element of the ferroelectric is dissolved in a solvent, and the sixth raw material liquid is a constituent metal element of the ABO-based oxide. The metal compound or metal inorganic compound can be dissolved in a solvent.

(H) The eighth method for producing a ceramic film of the present invention is as follows.
Including a step of forming a raw material body layer in which a plurality of raw material layers are laminated, and a step of forming a ceramic film by crystallizing the raw material body layer,
The uppermost raw material layer in the raw material body layer has a crystallization temperature lower than that of the lower raw material layer in contact with the uppermost raw material layer, and the resulting crystal does not have a layered structure.

  According to the present invention, the crystal generated by the uppermost raw material layer functions as a seed layer in the crystallization of the lower raw material layer. In addition, since the uppermost raw material layer does not have a layered structure, the surface morphology of the ceramic film can be improved.

  The lower raw material layer in contact with the uppermost raw material layer is provided on the base via the first raw material layer, and the first raw material layer is the lower raw material layer in contact with the uppermost raw material layer. The crystallization temperature may be lower than that of the raw material layer. Thereby, the crystal | crystallization produced | generated based on the 1st raw material layer will function as a seed layer in crystallization of the lower raw material layer which contacts the uppermost raw material layer.

(I) The ninth method for producing a ceramic film of the present invention comprises:
A step of forming a raw material body layer including a raw material laminate in which a first raw material layer, a second raw material layer and a third raw material layer are laminated in this order; and, by crystallizing the raw material body layer, ceramics Forming a film,
The second raw material layer has a lower crystallization temperature than the first raw material layer and the third raw material layer.

  According to the present invention, the crystal generated based on the second raw material layer serves as a stopper for stopping crystal growth of the crystals of the first raw material layer and the third raw material layer. For this reason, the grain size of the crystal | crystallization produced | generated based on the 1st raw material layer and the 3rd raw material layer can be made small.

  A fourth raw material layer may be further laminated on the third raw material layer, and the fourth raw material layer may have a lower crystallization temperature than the third raw material layer. In the case of this aspect, the crystal generated based on the fourth raw material layer functions as a seed layer in the crystallization of the third raw material layer.

(J) The tenth method for producing a ceramic film of the present invention comprises:
Including a step of forming a raw material body layer in which a plurality of raw material layers are laminated, and a step of forming a ceramic film by crystallizing the raw material body layer,
The uppermost raw material layer in the raw material body layer has a higher crystallization temperature than the lower raw material layer in contact with the uppermost raw material layer.

  According to the present invention, the crystal generated based on the uppermost raw material layer can be formed so as to cover the crystal generated based on the lower raw material layer.

  In the uppermost raw material layer in the raw material body layer, it is preferable that the obtained crystal does not have a layered structure. Thereby, the surface morphology of the ceramic film can be improved.

  In the first to tenth ceramic film manufacturing methods of the present invention, the step of forming the ceramic film can be performed a plurality of times by crystallizing the raw material body.

(Ceramics film)
The ceramic film of the present invention is obtained by the method for producing a ceramic film of the present invention.

(Application example of ceramic film)
The semiconductor device of the present invention has a capacitor including the ceramic film of the present invention.

  The piezoelectric element of the present invention includes the ceramic film of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
(Ceramic film manufacturing method)
Hereinafter, the manufacturing method of the ceramic film which concerns on embodiment is demonstrated. FIG. 1 is a cross-sectional view schematically showing a manufacturing process of a ceramic film according to an embodiment. In particular, FIG. 1B is a conceptual diagram showing the concept of the crystallization mechanism.

  (1) As shown in FIG. 1A, a raw material body 20 is formed on a base 10. Examples of a method for forming the raw material body 20 on the substrate 10 include a coating method and an LSMCD method. Examples of the coating method include a spin coating method and a dipping method. The raw material body 20 includes a sol-gel raw material and a MOD raw material. As the sol-gel raw material, a raw material having a lower crystallization temperature, a higher crystal nucleus formation rate and a higher crystal growth rate than the MOD raw material is selected.

Specifically, the sol-gel raw material can be prepared as follows. First, a metal alkoxide having 4 or less carbon atoms is mixed and subjected to hydrolysis and polycondensation. By this hydrolysis and polycondensation, a strong bond of M-O-M-O ... can be formed. The M-O-M bond structure obtained at this time has a structure close to the ceramic crystal structure (perovskite structure). Here, M is a metal element (for example, Bi, Ti, La, Pb), and O represents oxygen. The ratio of the metal element and the metal element is selected and determined according to the ceramic to be obtained. Taking BiLaTiO-based (hereinafter referred to as “BLT”) ceramics as an example, the ratio is Bi _3.25 La _0.75 Ti ₃ O _X. In addition, since O is not a value finally obtained, it is set to X. Next, a solvent is added to the product obtained by performing hydrolysis and polycondensation to obtain a raw material. Thus, the sol-gel raw material can be prepared.

  Examples of the MOD raw material include a polynuclear metal complex raw material in which constituent elements of ceramics are continuously connected directly or indirectly. Specific examples of the MOD raw material include metal salts of carboxylic acids. Examples of the carboxylic acid include acetic acid and 2-ethylhexanoic acid. Examples of the metal include Bi, Ti, La, and Pb. The MOD raw material (polynuclear metal complex raw material) also has an M—O bond, like the sol-gel raw material. However, the MO bond is not a continuous bond like the sol-gel raw material obtained by polycondensation, and the bond structure is also close to the linear structure and far from the perovskite structure.

  Next, the raw material body 20 is dried as necessary.

  (2) Next, as shown in FIG. 1C, the raw material body 20 is heat-treated to crystallize the raw material body 20 to form a ceramic film 30. The crystallization of the raw material body 20 is performed under the condition that the sol-gel raw material and the MOD raw material are crystallized independently of each other at least in the initial stage of crystal growth, and the first crystal 42 resulting from the sol-gel raw material and the MOD raw material And the second crystal 52 resulting from the above.

  A specific example of the crystallization mechanism of the sol-gel raw material and the MOD raw material will be described. The sol-gel raw material has a lower crystallization temperature than the MOD raw material. The sol-gel raw material has a higher crystal nucleus formation rate and crystal growth rate than the MOD raw material. Therefore, by controlling the temperature or the like, the crystallization of the sol-gel raw material can be advanced prior to the crystallization of the MOD raw material. As the crystallization of the sol-gel raw material proceeds prior to the crystallization of the MOD raw material, the MOD raw material remains in the gap between the first crystals 42 caused by the sol-gel raw material as shown in FIG. For this reason, the second crystal 52 caused by the MOD raw material grows in the gap between the first crystals 42 caused by the sol-gel raw material. Thus, the first crystal 42 and the second crystal 52 grow independently of each other. That is, the second crystal 52 grows so as to fill the gap between the first crystals 42. The sol-gel raw material and the MOD raw material differ in the direction in which crystals are easily oriented. Therefore, the growth is mutually cut off and it is easy to crystallize. When the crystal is microcrystallized, there is an effect of reducing the gap between the crystals. As a result, the ceramic film 30 with improved surface morphology can be formed.

  Hereinafter, specific conditions for crystallization of the raw material body will be described.

  Examples of the heat treatment method include a method of annealing in an oxygen atmosphere using RTA and FA (furnace).

  More specific raw material body crystallization conditions are as follows. First, annealing is performed for 5 to 30 seconds at a temperature of 500 to 650 ° C. using RTA to generate microcrystal nuclei. At this time, crystal nuclei made of a sol-gel raw material are generated first. In the process of growing crystals made of sol-gel raw material, crystal nuclei made of MOD raw material grow around it. Next, the ceramic film 30 is obtained by accelerating crystallization at 600 to 650 ° C. for 10 to 30 minutes using FA.

(Modification)
The ceramic film manufacturing method according to the above embodiment can be modified as follows, for example.

  (1) The combination of raw materials is not limited to the above embodiment, and for example, the following combinations are possible.

  1) A plurality of sol-gel raw materials having different degrees of polycondensation can be used. Even in the same composition, if the degree of polycondensation is different, the direction of crystal growth is generally different. For this reason, when raw materials having different degrees of polycondensation are mixed, the orientation in which crystal growth is likely to occur is different, so that the crystal growth is blocked and microcrystallization can be achieved.

  2) Raw materials having compositions having different crystal structures can be used. For example, raw materials having the following relationship can be used.

When the ceramics obtained from the raw materials are represented as (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ²⁻ , raw materials having different m can be used. Examples of m = 1 include Bi ₂ WO ₆ , examples of m = 2 include Bi ₃ TiNbO ₉ , and examples of m = 3 include Bi ₄ Ti ₃ O ₁₂ . These are all ferroelectrics but have different crystal structures. That is, the difference between the lengths a and b is small, but the c-axis has m = 1 of 16.4 mm (1.64 nm), m = 2 of 25.0 mm (2.50 nm), and m = 3. Is 32.8 mm (3.28 nm). Since these have different crystal structures, the raw materials for producing these crystals have different crystal growth conditions and crystal growth mechanisms.

  In addition, when using a composition raw material from which a crystal structure differs, it is preferable to make a B site element common between different raw materials for the following reasons. That is, even if different crystal growth conditions and different crystal growth mechanisms are used to crystallize different raw materials independently of each other, interdiffusion occurs not less than in the vicinity of the grain boundary in the subsequent long annealing process. In this case, if the B-site element is substituted, the ceramic characteristics tend to deteriorate.

3) A combination of a raw material whose crystal structure is Bi ₄ Ti ₃ O ₉ (hereinafter referred to as “BTO raw material”) and a raw material whose crystal structure is PbTiO ₃ (hereinafter referred to as “PTO raw material”). Can be mentioned. PbTiO ₃ is a tetragonal perovskite. However, PTO has little difference between the a-axis and c-axis, and the crystal growth anisotropy due to the crystal structure is small. In addition, the formation of crystal nuclei in the PTO raw material is easily generated at a relatively low temperature. Therefore, when the PTO raw material is mixed with the BTO raw material in a small ratio, for example, at a ratio of about 10: 1, the crystal growth is blocked. For this reason, there is an effect that the obtained crystal is microcrystallized. This effect is more significant than crystals having the same layered perovskite structure.

  4) You may combine the raw material which produces a ferroelectric crystal, and the raw material which produces a paraelectric crystal. The mixing amount is determined according to the desired characteristics of the ceramic film.

  5) A combination of a sol-gel raw material and a MOD raw material, wherein the crystal structures of the crystals generated by the respective raw materials are different from each other.

  6) A combination of sol-gel raw materials having different degrees of polycondensation, and a combination of raw materials having different crystal structures of crystals produced by the respective raw materials.

  (2) The ceramic film can be formed by carrying out the method for producing a ceramic film of the present invention a plurality of times. Moreover, a ceramic film can be formed by combining the method for producing a ceramic film of the present invention and a known method for producing a ceramic film.

  (3) Examples of a method for forming a raw material body on a substrate by the LSMCD method include the following methods. FIG. 3 is a cross-sectional view schematically showing an apparatus 200 for forming a raw material body on a substrate by the LSMCD method.

  The first raw material 210 is sent to the mesh 240 by the sprayer 230. The first raw material 210 that has passed through the mesh 240 becomes a mist 250 and is supplied onto the substrate 10. The second raw material 220 is also sent to the mesh 240 by the sprayer 232, and the second raw material 220 that has passed through the mesh 240 becomes a mist 250 and is supplied onto the base 10. Thus, the raw material body is formed by the mist 250 being stacked on the base 10. The particle size of the mist 250 is, for example, 10 to 200 nm.

  The first raw material 210 and the second raw material 220 can be simultaneously supplied onto the substrate 10. Alternatively, the first raw material 210 and the second raw material 220 may be supplied alternately.

  When the first raw material 210 and the second raw material 220 are simultaneously supplied onto the base 10, the raw material body is, for example, a first material resulting from the first raw material 210 as shown in FIG. The mist 210a and the second mist 220a caused by the second raw material 220 are mixed.

  When the first raw material 210 and the second raw material 220 are supplied alternately, the raw material body is, for example, as shown in FIG. 4B, a first mist 210a caused by the first raw material 210 and Each of the second mists 220a resulting from the second raw material 220 constitutes one layer. That is, the same layer is comprised from the mist resulting from the same raw material.

[Second Embodiment]
(First ceramic raw material liquid)
The first ceramic raw material liquid is a raw material liquid used by mixing the first raw material liquid and the second raw material liquid. The first ceramic raw material liquid can be a raw material liquid from which a ceramic film can be obtained by thermal decomposition. The first raw material liquid and the second raw material liquid have a relationship of different types of materials to be generated. The first and second raw material liquids are, for example, 1) a metal organic compound (eg, metal alkoxide, metal carboxylic acid) or a metal inorganic compound (eg, metal nitrate, metal chloride) as a solvent (eg, water, alcohol, ester, fat) Liquids dissolved in aromatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, or mixtures thereof), 2) liquids in which a metal compound is hydrolyzed or condensed in a solvent, 3) metal alkoxides It can be a sol-gel solution obtained by hydrolysis.

  Hereinafter, the first raw material liquid and the second raw material liquid will be specifically described.

The first raw material liquid is a raw material liquid for generating a ferroelectric having a Bi-based layered perovskite structure. Examples of ferroelectrics having a Bi-based layered perovskite structure include SrBiTaO-based ferroelectrics (for example, SrBi ₂ Ta ₂ O ₉ ), BiLaTiO-based ferroelectrics (for example, Bi _3.25 La _0.75 Ti ₃ O ₁₂ ), and BiTiO-based ferroelectrics. A ferroelectric substance (for example, Bi ₄ Ti ₃ O ₁₂ ) can be mentioned. The first raw material liquid contains a metal element constituting the ferroelectric. The amount of the constituent metal element of the ferroelectric contained in the first raw material liquid takes into consideration the amount of the desired ferroelectric and the ratio of the number of atoms of the constituent metal element in the desired ferroelectric. Determined.

As a specific example of the first raw material liquid, in the case of an SrBiTaO-based ferroelectric, a liquid in which respective solutions of strontium alkoxide, bismuth alkoxide, and tantalum alkoxide are mixed in 2-methoxyethanol. it can. In the first raw material liquid, the concentrations of strontium alkoxide, bismuth alkoxide, and tantalum alkoxide are, for example, 0.05 mol / l, 0.1 mol / l, and 1.0 mol / l, respectively. it can. That is, each concentration can be set so that 0.05 mol of SrBi ₂ Ta ₂ O ₉ ferroelectric is generated per liter of the first raw material liquid.

The second raw material liquid is a raw material liquid for generating an ABO-based oxide whose A site is Bi. If the A site is not Bi, elements other than Bi may be accommodated at the site where Bi of the Bi-based layered perovskite structure should be accommodated, which may adversely affect the characteristics of the ferroelectric film. Examples of the ABO oxide in which the A site is Bi include a BiGeO oxide (for example, Bi ₄ Ge ₃ O ₁₂ ), a BiMoO oxide (Bi ₂ MoO ₆ ), and a BiVO oxide (Bi ₂ VO _6). ), BiCrO-based oxide (Bi ₂ CrO ₆ ), BiSiO-based oxide (Bi ₄ Si ₃ O ₁₂ ), and BiWO-based oxide (Bi ₄ W ₃ O ₁₂ ). Note that the crystallization temperature of crystals based on the second raw material liquid can be changed by changing the element at the B site of the ABO-based oxide. In addition, the ABO-based oxide may be a ferroelectric or a paraelectric.

  The second raw material liquid contains a metal element constituting the ABO-based oxide. The amount of the constituent metal element of the ABO-based oxide contained in the second raw material liquid is the amount of the desired ABO-based oxide and the number of atoms of the constituent metal element in the desired ABO-based oxide. It is determined in consideration of the ratio.

As a specific example of the second raw material liquid, in the case of a BiGeO-based oxide, a liquid in which respective solutions of bismuth alkoxide and germanium alkoxide are mixed in 2-methoxyethanol. The concentrations of bismuth alkoxide and germanium alkoxide in the second raw material liquid can be, for example, 0.20 mol / l and 0.15 mol / l, respectively. That is, each concentration of bismuth alkoxide and germanium alkoxide can be set so that 0.05 mol of Bi ₄ Ge ₃ O ₁₂ oxide is produced per liter of the second raw material liquid.

  The first raw material liquid and the second raw material liquid have a molar ratio of 100% of the ferroelectric obtained based on the first raw material liquid and the ABO-based oxide obtained based on the second raw material liquid. : It is preferable to mix so that it may become 20-100: 100. The reason for this will be described in the example section.

(Manufacturing example of ceramic film)
Using the ceramic raw material liquid according to the present embodiment, for example, a ceramic film can be manufactured as follows. In addition, as a schematic cross-sectional view schematically showing the manufacturing process of the ceramic film, the manufacturing process of the ceramic film will be described using FIG. 1 as in the first embodiment.

  (A) First, the substrate 10 is heat-treated. This heat treatment is performed to remove moisture on the surface of the substrate 10. The temperature of heat processing is 180 degreeC, for example.

  (B) Next, a ceramic raw material solution is applied onto the substrate 10 to form the ceramic raw material body layer 20. Examples of the forming method include spin coating, dipping, and LSMCD.

  (C) Next, a drying heat treatment is performed to evaporate the solvent in the ceramic raw material layer 20. The evaporation of the solvent can be performed under a nitrogen atmosphere. The temperature of the drying heat treatment is 160 ° C., for example.

  (D) Next, the ceramic raw material body layer 20 is subjected to a degreasing heat treatment. By this heat treatment, the organic matter in the ceramic raw material body layer 20 can be decomposed. The decomposition of the organic substance can be performed in a nitrogen atmosphere. The temperature of this heat treatment is 260 ° C., for example.

  (E) Next, the ceramic raw material body layer 20 is temporarily sintered. In this preliminary sintering, crystal nuclei are formed. The preliminary sintering can be performed by RTA, for example, in an oxygen atmosphere.

  (F) Next, the ceramic raw material layer 20 is sintered. This sintering can be performed by, for example, FA (furness) in an oxygen atmosphere.

  Note that the steps (a) to (e) may be set as one cycle, and this cycle may be performed a plurality of times.

(Function and effect)
Hereinafter, the operation and effect when the ceramic film is formed using the ceramic raw material liquid according to the second embodiment will be described.

  (1) In the case of forming a ferroelectric (SBT) film by firing a ceramic raw material liquid consisting of only the first raw material liquid, generally, if the firing temperature is not about 700 ° C., the ferroelectric film The desired characteristics (for example, remanent polarization) required for the above cannot be obtained.

  However, when the first ceramic raw material liquid is baked and the ceramic film is formed in a state where the first raw material liquid and the second raw material liquid are mixed, as described later, the temperature is about 500 ° C. Desired characteristics required for the ferroelectric film can be obtained even at the firing temperature. That is, according to the present embodiment, a ferroelectric film having desired characteristics can be formed at a lower temperature.

  (2) The material generated based on the first raw material liquid is different from the material generated based on the second raw material liquid. For this reason, for example, the crystallization temperature at which the first raw material liquid crystallizes differs from the crystallization temperature at which the second raw material liquid crystallizes. As a result, the crystallization of one raw material liquid can precede the crystallization of the other raw material liquid. Therefore, as shown in FIG. 1B, a crystal 52 based on the other raw material liquid can be grown between the crystals 42 based on the one raw material liquid. In other words, the crystal 42 based on one raw material liquid and the crystal 52 based on the other raw material grow independently, and the crystal 52 based on the other raw material fills the space between the crystals 42 based on the one raw material liquid. Will grow. As a result, a ceramic film with improved surface morphology can be formed.

  (3) Also, by changing the direction in which crystals based on the second raw material liquid are easily oriented from the direction in which crystals based on the first raw material liquid are easily oriented, crystal growth of crystals based on one raw material liquid can be improved. The other crystal is obstructed by the crystal growth. For this reason, in this case, the crystal of the obtained ceramic film can be microcrystallized. As a result, a ceramic film with improved surface morphology can be formed.

(Modification)
The second embodiment described above can be modified as follows.

  (1) The ceramic film can be formed by performing the above-described ceramic film manufacturing process a plurality of times. Moreover, a ceramic film can be formed by combining the above-described ceramic film manufacturing process and a process of manufacturing a ceramic film from a known ceramic raw material.

  (2) Examples of a method for forming a raw material body on a substrate by the LSMCD method include the following methods. FIG. 3 is a cross-sectional view schematically showing an apparatus 200 for forming a raw material body on a substrate by the LSMCD method.

  The first raw material liquid 210 is sent to the mesh 240 by the sprayer 230. The first raw material liquid 210 that has passed through the mesh 240 becomes a mist 250 and is supplied onto the substrate 10. The second raw material liquid 220 is also sent to the mesh 240 by the sprayer 232, and the second raw material liquid 220 that has passed through the mesh 240 becomes the mist 250 and is supplied onto the substrate 10. Thus, the raw material body is formed by the mist 250 being stacked on the base 10. The particle size of the mist 250 is, for example, 10 to 200 nm.

  The first raw material liquid 210 and the second raw material liquid 220 can be simultaneously supplied onto the substrate 10. Alternatively, the first raw material liquid 210 and the second raw material liquid 220 can be supplied alternately.

  When the first raw material liquid 210 and the second raw material liquid 220 are simultaneously supplied onto the substrate 10, the raw material body is caused by the first raw material liquid 210, for example, as shown in FIG. The first mist 210a and the second mist 220a resulting from the second raw material liquid 220 are mixed.

  In the case where the first raw material liquid 210 and the second raw material liquid 220 are alternately supplied, the raw material body is, for example, as shown in FIG. The mist 210a and the second mist 220a resulting from the second raw material liquid 220 each constitute one layer. That is, the same layer is comprised from the mist resulting from the same raw material.

[Third Embodiment]
(Second ceramic raw material liquid)
The second ceramic raw material liquid is a solution used by mixing the third raw material liquid and the fourth raw material liquid. The second ceramic raw material liquid can be a raw material liquid from which a ceramic film can be obtained by thermal decomposition. The third raw material liquid and the fourth raw material liquid have a relationship in which the types of materials to be generated are different. The third and fourth raw material liquids are, for example, 1) a metal organic compound (eg, metal alkoxide, metal carboxylic acid) or a metal inorganic compound (eg, metal nitrate, metal chloride) as a solvent (eg, water, alcohol, ester, fat) Liquids dissolved in aromatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, or mixtures thereof), 2) liquids in which a metal compound is hydrolyzed or condensed in a solvent, 3) metal alkoxides It can be a sol-gel solution obtained by hydrolysis.

  Hereinafter, the third raw material liquid and the fourth raw material liquid will be specifically described.

The third raw material liquid is a raw material liquid for generating a PZT-based ferroelectric. The ferroelectric PZT system ferroelectric PbZrTiO-based (e.g. _{PbZr y Ti 1-y O 3} ), ferroelectric PbLaZrTiO system (e.g. _{Pb 1 -x La x Zr y Ti} 1-y O 3) Can be mentioned. The third raw material liquid contains a metal element constituting the ferroelectric. The amount of the constituent metal element of the ferroelectric contained in the third raw material liquid takes into consideration the amount of the desired ferroelectric and the ratio of the number of atoms of the constituent metal element in the desired ferroelectric. Determined.

  As a specific example of the third raw material liquid, when a PbZrTiO-based ferroelectric is taken as an example, a liquid containing lead acetate trihydrate, zirconium butoxide, and titanium isopropoxide in 1-methoxy-2-propanol Can be mentioned. The amount of lead acetate trihydrate, zirconium butoxide, titanium isopropoxide is used in consideration of the ratio of the number of constituent metal elements in the desired ferroelectric and the amount of the desired ferroelectric. It is determined.

The fourth raw material liquid is a raw material liquid for generating an ABO-based oxide whose A site is Pb. If the A site is not Pb, an element other than Pb may be accommodated at the site where Pb of the PZT-based oxide should be accommodated, which may adversely affect the characteristics of the ferroelectric film. Examples of the ABO oxide whose A site is Pb include PbGeO oxide (Pb ₅ Ge ₃ O ₁₁ ), PbMoO oxide (Pb ₂ MoO ₅ ), and PbVO oxide (Pb ₂ VO ₅ ). PbCrO-based oxide (Pb ₂ CrO ₅ ), PbSiO-based oxide (Pb ₅ Si ₃ O ₁₁ ), PbWO-based oxide (Pb ₂ WO ₅ ), PbSnO-based oxide (PbSnO ₃ ), PbGeSiO An oxide (Pb ₅ Ge ₂ SiO ₁₁ ) can be used. Note that by changing the element at the B site of the ABO-based oxide, the crystallization temperature of the crystal based on the fourth raw material liquid can be changed. In addition, the ABO-based oxide may be a ferroelectric or a paraelectric.

  As a specific example of the fourth raw material liquid, when a PbGeO-based oxide is taken as an example, a liquid in which germanium ethoxide and lead butoxide are dissolved in 1-methoxy-2-propanol can be exemplified. The amount of germanium ethoxide and lead butoxide used is determined in consideration of the ratio of the number of constituent metal elements of the desired oxide and the desired amount of oxide.

  The third raw material liquid and the fourth raw material liquid have a molar ratio of 100% of the ferroelectric obtained based on the third raw material liquid and the ABO-based oxide obtained based on the fourth raw material liquid. : It is preferable to mix so that it may become 20-100: 100.

(Example of production of second ceramic film)
The film forming method of the second ceramic raw material liquid can be the method shown in the second embodiment.

(Function and effect)
Hereinafter, the operation and effect when the ceramic film is formed using the ceramic raw material liquid according to the third embodiment will be described.

  (1) According to the ceramic raw material liquid according to the present embodiment, in the case where the ferroelectric film is formed by baking only the third raw material liquid, it is higher than the baking temperature necessary for producing predetermined characteristics. A ferroelectric film having predetermined characteristics can be formed at a low firing temperature. That is, according to the present embodiment, a ferroelectric film having desired characteristics can be formed at a lower temperature.

  (2) The material generated based on the third raw material liquid is different from the material generated based on the fourth raw material liquid. For this reason, for example, the crystallization temperature at which the third raw material liquid crystallizes differs from the crystallization temperature at which the fourth raw material liquid crystallizes. As a result, a ceramic film with improved surface morphology can be formed as in the second embodiment.

  The third embodiment can take the modification shown in the second embodiment.

[Fourth Embodiment]
(3rd ceramic raw material liquid)
The third ceramic raw material liquid is a raw material liquid used by mixing the fifth raw material liquid and the sixth raw material liquid. The third ceramic raw material liquid can be a raw material liquid from which a ceramic film can be obtained by thermal decomposition. The fifth raw material liquid and the sixth raw material liquid have a relationship of different types of materials to be generated. The fifth and sixth raw material liquids are, for example, 1) a metal organic compound (eg, metal alkoxide, metal carboxylic acid) or a metal inorganic compound (eg, metal nitrate, metal chloride) as a solvent (eg, water, alcohol, ester, fat) Liquids dissolved in aromatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, or mixtures thereof), 2) liquids in which a metal compound is hydrolyzed or condensed in a solvent, 3) metal alkoxides It can be a sol-gel solution obtained by hydrolysis.

  Hereinafter, the fifth raw material liquid and the sixth raw material liquid will be specifically described.

  The fifth raw material liquid is a raw material liquid for generating a ferroelectric having a Bi-based layered perovskite structure or a PZT-based ferroelectric. As the ferroelectric having the Bi-based layered perovskite structure, those shown in the first ceramic raw material liquid can be applied. As the PZT-based ferroelectric, those shown in the first ceramic raw material liquid can be applied. As a specific example of the fifth raw material liquid, in the case of a ferroelectric having a Bi-based layered perovskite structure, a specific example of the first raw material liquid (second embodiment) can be applied. In the case of a body, a specific example of the third raw material liquid (third embodiment) can be applied.

The sixth raw material liquid is a raw material liquid for generating an AGeO-based oxide. Since the oxide whose B site is Ge has a low melting point of around 700 ° C., the temperature of the process can be lowered. Examples of the A site in the AGeO-based oxide include alkaline earth metals, rare earth elements (particularly Ce), Zr, Sr, and Bi. Examples of the ZrGeO-based oxide include ZrGeO ₄ , and examples of the SrGeO-based oxide include Sr ₅ Ge ₃ O ₁₁ . As a specific example of the sixth raw material liquid, in the case of a BiGeO-based oxide, a specific example of the second raw material liquid (second embodiment) can be applied. The AGeO-based oxide may be a paraelectric material or a ferroelectric material.

  The fifth raw material liquid and the sixth raw material liquid have a molar ratio of the ferroelectric obtained based on the fifth raw material liquid and the ABO-based oxide obtained based on the sixth raw material liquid of 100. : It is preferable to mix so that it may become 20-100: 100.

(Example of third ceramic film production)
The film formation method of the third ceramic raw material liquid may be the method shown in the film formation method of the first ceramic raw material liquid.

(Function and effect)
Hereinafter, the operation and effect when the ceramic film is formed using the ceramic raw material liquid according to the fourth embodiment will be described.

  (1) According to the ceramic raw material liquid according to the present embodiment, when only the fifth raw material liquid is fired to form the ferroelectric film, the firing temperature is higher than the firing temperature necessary for producing predetermined characteristics. A ferroelectric film having predetermined characteristics can be formed at a low firing temperature. That is, according to the present embodiment, a ferroelectric film having desired characteristics can be formed at a lower temperature.

  (2) The material generated based on the fifth raw material liquid is different from the material generated based on the sixth raw material liquid. For this reason, for example, the crystallization temperature at which the fifth raw material liquid crystallizes differs from the crystallization temperature at which the sixth raw material liquid crystallizes. As a result, a ceramic film with improved surface morphology can be formed as in the second embodiment.

  (3) Also, by changing the direction in which crystals based on the sixth raw material liquid are easily oriented from the direction in which crystals based on the fifth raw material liquid are easily oriented, the crystal growth of the crystals based on one raw material liquid can be improved. The other crystal is obstructed by the crystal growth. For this reason, in this case, the crystal of the obtained ceramic film can be microcrystallized. As a result, a ceramic film with improved surface morphology can be formed.

  The fourth embodiment can take the modification shown in the second embodiment.

[Fifth Embodiment]
Hereinafter, a manufacturing example of the multilayer ceramic film according to the fifth embodiment will be described.

(Example of production of first multilayer ceramic film)
Hereinafter, a manufacturing example of the first multilayer ceramic film will be described. FIG. 5 is a cross-sectional view schematically showing the manufacturing process of the first multilayer ceramic film.

  First, as shown in FIG. 5A, a main liquid layer 312 for generating a ferroelectric material is formed on a substrate 10 by a coating method. Examples of the material of the main liquid layer 312 include the first raw material liquid in the second embodiment and the third raw material liquid in the third embodiment.

  Next, a sub liquid layer 322 for generating a ferroelectric material or a paraelectric material is formed on the main liquid layer 312. Note that the material of the secondary liquid layer 322 is selected to have a lower crystallization temperature than the material of the main liquid layer 312. In addition, as a material for the secondary liquid layer 322, a material that generates an oxide having no layered structure after crystallization is selected. The material of the secondary liquid layer 322 varies depending on the material of the main liquid layer 312, but when the SBT ferroelectric is generated when the main liquid layer 312 is crystallized, the material of the secondary liquid layer 322 is: For example, BiGeO system, BiSiO system, SrGeO system.

  Next, by performing heat treatment, as shown in FIG. 5C, the main liquid layer 312 and the sub liquid phase 322 are crystallized, and the ceramic film 300 including the main crystal layer 310 and the sub crystal layer 320 is formed. Form.

  According to the manufacturing example of the first multilayer ceramic film, the following operational effects can be obtained.

  For the secondary liquid layer 322, a material having a lower crystallization temperature than that of the main liquid layer 312 is selected. For this reason, in the initial stage of crystallization, as shown in FIG. 5B, the crystallization of the sub-liquid layer 322 preferentially proceeds with respect to the main liquid layer 312. As a result, crystals generated in the secondary liquid layer 322 function as seeds in the crystallization of the main liquid layer 312. Therefore, the crystallization of the main liquid layer 312 proceeds from the sub liquid layer 322 side and the substrate 10 side. For this reason, the grain size of crystals in the main liquid layer 312 can be reduced.

  In addition, as a material for the secondary liquid layer 322, a material that generates an oxide that does not have a layered structure after crystallization is used. For this reason, crystals grow isotropically in the sub-liquid layer 322. As a result, the subcrystalline layer 320 having a flat surface is formed, and the surface morphology of the ceramic film 300 can be improved.

  As shown in FIG. 6A, a ceramic film 300 composed of a main crystal layer 310 and sub crystal layers 320 and 330 with a sub liquid layer 332 interposed between the base 10 and the main liquid layer 312. Can also be formed.

(Example of production of second multilayer ceramic film)
Hereinafter, a production example of the second multilayer ceramic film will be described. FIG. 7 is a cross-sectional view schematically showing the manufacturing process of the second multilayer ceramic film.

  The production example of the second multilayer ceramic film is different from the production example of the first multilayer ceramic film in that a sub liquid layer 422 is interposed between the main liquid layers 412 and 432.

  That is, the main liquid layer 412, the sub liquid layer 422, the main liquid layer 432, and the sub liquid layer 442 are sequentially stacked on the substrate 10. Then, by crystallizing these layers, the ceramic film 400 composed of the main crystal layers 410 and 430 and the sub crystal layers 420 and 440 is formed.

  The secondary liquid layers 422 and 442 are selected from materials having a lower crystallization temperature than the main liquid layers 412 and 442, as in the first multilayer ceramic film manufacturing example.

  Thus, by interposing the sub liquid layer 422 between the main liquid layers 412 and 432, the crystals generated in the sub liquid layer 422 serve as a stopper for stopping crystal growth of the crystals in the main liquid layers 412 and 432. . Therefore, the crystal grain size of the main crystal layers 410 and 430 on both sides of the sub crystal layer 420 can be reduced.

(Example of production of third multilayer ceramic film)
Hereinafter, a production example of the second multilayer ceramic film will be described. FIG. 8 is a cross-sectional view schematically showing the manufacturing process of the third multilayer ceramic film.

  The production example of the third multilayer ceramic film is different from the production example of the first multilayer ceramic film in that the material of the main liquid layer 512 is a material having a lower crystallization temperature than the material of the sub-liquid layer 522.

  In this case, examples of the material of the main liquid layer 512 include the first raw material liquid in the second embodiment and the third raw material liquid in the third embodiment. When the material of the main liquid layer 512 is one that generates a PZT-based ferroelectric, the material of the sub-liquid layer 522 can be PbWO-based or PbMoO-based.

  By crystallizing the main liquid layer 512 and the sub liquid layer 522, a ceramic film with improved surface morphology can be formed. The reason for this is as follows. The material of the main liquid layer 512 is made of a material having a lower crystallization temperature than the material of the sub liquid layer 522. Therefore, the crystallization of the secondary liquid layer 522 proceeds with a delay with respect to the main liquid layer 512 and is based on the secondary liquid layer 522 so as to cover the main crystal layer 510 formed based on the main liquid layer 512. Crystals are produced. Since the crystals generated based on the sub liquid layer 522 do not have a layered structure, the crystals based on the sub liquid layer 522 grow isotropically. For this reason, the sub-crystal layer 520 whose surface is planarized is formed. As a result, unevenness is reduced on the surface of the ceramic film 500, and the surface morphology of the ceramic film 500 can be improved.

  In the manufacturing examples of the first to third multilayer ceramic films, the crystal grains based on the main liquid layer and the crystal grains based on the sub liquid layer may be diffused in different crystal layers. Further, the constituent metal element in the main liquid layer may diffuse into the sub liquid layer, or the constituent metal element in the sub liquid layer may diffuse into the main liquid layer. For this reason, the interface between the main crystal layer formed based on the main liquid layer and the sub crystal layer formed based on the sub liquid layer may not be clear.

[Sixth Embodiment]
(Semiconductor device)
Hereinafter, a semiconductor device to which a ceramic film obtained by the method for producing a ceramic film of the present invention is applied will be described. In this embodiment, an example of a ferroelectric memory device is shown as a semiconductor device. FIG. 2 is a cross-sectional view schematically showing a ferroelectric memory device.

  The ferroelectric memory device 5000 has a CMOS region R1 and a capacitor region R2 formed on the CMOS region R1. That is, the CMOS region R1 includes the semiconductor substrate 1, the element isolation region 2 and the MOS transistor 3 formed on the semiconductor substrate 1, and the interlayer insulating layer 4. The capacitor region R2 includes a capacitor C100 composed of the lower electrode 5, the ferroelectric film 6 and the upper electrode 7, a wiring layer 8a connected to the lower electrode 5, a wiring layer 8b connected to the upper electrode 7, And an insulating layer 9. The ferroelectric film 6 in the capacitor C100 is formed by the ceramic film manufacturing method of the present invention. The impurity diffusion layer 3a of the MOS transistor 3 and the lower electrode 5 constituting the capacitor 5 are connected by a contact layer 11 made of polysilicon or tungsten.

  Hereinafter, the function and effect of the ferroelectric device will be described.

(1) When a ferroelectric film is formed, it is necessary to increase the thickness of the ferroelectric film because it is necessary to prevent a short circuit between the upper electrode and the lower electrode in consideration of the formation of grooves and holes. is there. This short circuit between the upper electrode and the lower electrode occurs remarkably when the upper electrode is made of an iridium-based material (Ir, IrO ₂ ). However, in the present embodiment, the ferroelectric film 6 of the ferroelectric device 5000 is formed by the ceramic film manufacturing method of the present invention. For this reason, the surface morphology of the ferroelectric film 6 is improved. As a result, the thickness of the ferroelectric film 6 can be reduced by an amount corresponding to the improvement of the surface morphology in the ferroelectric film 6. Therefore, according to the ferroelectric device 5000, high integration can be achieved.

  Further, according to the present embodiment, the range of the film thickness of the ferroelectric film 6 to which an iridium material can be applied as the material of the upper electrode 7 can be expanded. That is, the limit of the thinnest thickness of the ferroelectric film 6 that can apply an iridium-based material as the material of the upper electrode 7 can be lowered.

  Note that the iridium-based material has an advantage of superior hydrogen barrier properties and fatigue characteristics as compared with platinum (Pt).

  (2) When the ferroelectric film is etched in a state in which the surface of the ferroelectric film is uneven, the uneven shape of the surface of the ferroelectric film is transferred to the surface of the lower electrode that is the base of the ferroelectric film. As a result, the surface morphology of the lower electrode deteriorates. When the surface morphology of the lower electrode deteriorates, a contact failure may occur between the wiring layer desired to be connected to the lower electrode and the lower electrode.

  However, in the present embodiment, the surface morphology of the ferroelectric film 6 is improved. For this reason, it is possible to suppress the deterioration of the surface morphology of the lower electrode 5 after etching the ferroelectric film 6. As a result, the wiring layer 8a can be reliably connected to the lower electrode 9 reliably.

(Modification)
A semiconductor device to which the ceramic film obtained by the method for producing a ceramic film of the present invention can be applied is not limited to a ferroelectric memory, and can be applied to various semiconductor devices, for example, DRAMs. Specifically, the ceramic film of the present invention can be applied to a dielectric film in a DRAM capacitor. In this case, the dielectric film can be made of a high dielectric constant paraelectric material such as BST from the viewpoint of increasing the capacity of the capacitor.

  The ceramic film obtained by the manufacturing method of the present invention can be applied not only to a semiconductor device but also to other uses, for example, a piezoelectric body of a piezoelectric element used for an actuator.

  Next, the present invention will be described in more detail with reference to examples. In addition, this invention is not restrict | limited to a following example, unless the summary is exceeded.

Example 1
The main liquid was obtained as follows. 1100 ml of a toluene solution having a concentration of bismuth 2-ethylhexanoate of 0.1 mol / l, 400 ml of a toluene solution having a concentration of strontium 2-ethylhexanoate of 0.1 mol / l, and a concentration of tantalum ethoxide of 0.1 mol / l A mixed solution was prepared by mixing 1000 ml of a toluene solution and 100 g of 2-ethylhexanoic acid. The mixture was heated to reflux at 120 ° C. for 1 hour under a nitrogen atmosphere, and the solvent was distilled off at normal pressure. To this was added toluene so that the oxide concentration as Sr _0.8 Bi _2.2 Ta ₂ O _x (SBT) was 0.1 mol / l to obtain a main liquid.

On the other hand, the secondary liquid was obtained as follows. To 2000 ml of a toluene solution having a concentration of bismuth 2-ethylhexanoate of 0.1 mol / l, 1500 ml of a toluene solution having a concentration of 0.1 mol / l of germanium ethoxide and 100 g of 2-ethylhexanoic acid were mixed. This solution was heated to reflux at 120 ° C. for 1 hour under a nitrogen atmosphere, and then the solvent was distilled off at atmospheric pressure. To this was added toluene so that the oxide concentration as Bi ₄ Ge ₃ O ₁₂ was 0.1 mol / l to obtain a secondary liquid.

  The obtained main liquid and secondary liquid were mixed to obtain seven types of mixed liquids having different mixing volume ratios. The mixing volume ratio of the main liquid to the secondary liquid in the mixed liquid was 100: 1, 100: 10, 100: 20, 100: 50, 100: 100, 100: 150, and 100: 200.

  Ferroelectric films were formed from each of these seven types of mixed solutions and solutions containing only the main solution.

  In addition, the film-forming method was performed by the method shown in FIG. A series of processes including a pretreatment heating process, a solution coating process, a drying heat treatment process, a degreasing heat treatment process, and a preliminary sintering process were performed twice. Finally, sintering was performed to form a film. Specific conditions will be described below. The pretreatment heating step was performed at 180 ° C. for 30 seconds. Application of the mixed solution was performed for 30 seconds with a spin coater (2100 rpm). The drying heat treatment was performed at 160 ° C. for 1 minute in a nitrogen atmosphere. The degreasing heat treatment step was performed at 260 ° C. for 4 minutes in a nitrogen atmosphere. The preliminary sintering was performed for 30 seconds in an oxygen atmosphere. The preliminary sintering temperature was the firing temperature shown in Table 1. Sintering was performed for 60 minutes in an oxygen atmosphere. The sintering temperature was the firing temperature shown in Table 1. Moreover, the thickness of the formed film was 50 nm.

The Pr (residual polarization value) of each ferroelectric film was measured. Table 1 shows the measurement results of Pr. The unit of Pr is μC / cm ² .

  When manufacturing a ferroelectric memory device in which SBT is a ferroelectric, it is difficult to manufacture a ferroelectric memory device having a certain degree of integration unless the firing temperature is 600 ° C. or lower. In the ferroelectric memory device, the ferroelectric capacitor preferably has a Pr of 7 or more. In Table 1, when the firing temperature is 600 ° C. or lower, the mixing volume ratio (main liquid: secondary liquid) having data of Pr of 7 or more is 100: 20 to 100: 100. For this reason, it is preferable that the mixing volume ratio of a main liquid and a secondary liquid exists in the range of 100: 20-100: 100.

The main liquid is prepared so that 0.1 mol of Sr _0.8 Bi _2.2 Ta ₂ O _x is produced per liter of the main liquid. The secondary liquid is also prepared so that 0.1 mol of Bi ₄ Ge ₃ O ₁₂ is produced per liter of the secondary liquid. For this reason, the mixing volume ratio of the main liquid and the sub-liquid is simultaneously Sr _0.8 Bi _2.2 Ta ₂ O _X generated based on the main liquid and Bi ₄ Ge ₃ O ₁₂ generated based on the sub-liquid. The molar ratio will be shown. Therefore, the main liquid and the secondary liquid have a molar ratio of Sr _0.8 Bi _2.2 Ta ₂ O _X generated based on the main liquid and Bi ₄ Ge ₃ O ₁₂ generated based on the secondary liquid of 100: It is preferable to mix so that it may become 20-100: 100.

  Moreover, when it consists only of a main liquid, unless the baking temperature is 700 degreeC or more, the predetermined characteristic regarding Pr will not come out. On the other hand, by mixing the sub-liquid with the main liquid, predetermined characteristics are exhibited with respect to Pr even at a firing temperature of about 500 ° C. Thus, it can be seen that the temperature can be lowered when the main liquid is mixed with the sub-liquid to form a film.

(Example 2)
The main liquid was obtained as follows. In 1000 ml of 2-methoxyethanol, 85.3 g of titanium isopropoxide and 139.2 g of bismuth butoxide were added. The 2-methoxyethanol was heated to reflux at 125 ° C. for 1 hour under a nitrogen atmosphere and then returned to room temperature. To this, 23.7 g of lanthanum isopropoxide was added and stirred at room temperature for 2 hours. Further, after adding 1.3 g of water and stirring at room temperature for 1 hour, 2-methoxyethanol was added to prepare an oxide concentration of Bi _3.25 La _0.75 Ti ₃ O ₁₂ to 0.07 mol / l, A main liquid was obtained.

On the other hand, the secondary liquid was obtained as follows. In 1000 ml of 2-methoxyethanol, 75.9 g of germanium ethoxide and 171.3 g of bismuth butoxide were added. The 2-methoxyethanol was heated to reflux at 125 ° C. for 1 hour under a nitrogen atmosphere and then returned to room temperature. After adding 1.3 g of water and stirring at room temperature for 1 hour, 2-methoxyethanol was added to prepare an oxide concentration as Bi ₄ Ge ₃ O ₁₂ of 0.07 mol / l. Got.

  The obtained main liquid and secondary liquid were mixed to obtain seven types of mixed liquids having different mixing ratios. The mixing ratio of the main liquid and the secondary liquid in the mixed liquid was 100: 1, 100: 10, 100: 20, 100: 50, 100: 100, 100: 150, and 100: 200.

  Ferroelectric films were formed from each of these seven types of mixed solutions and solutions containing only the main solution. The film forming method is the same as that in Example 1.

  In Example 2, the same tendency as in Example 1 was observed with respect to Pr.

(Example 3)
The main liquid was obtained as follows. In 100 ml of xylene, 81.2 g of tantalum ethoxide and 170 g of 2-ethylhexanoic acid are added, and 20.6 g of strontium isopropoxide is added thereto, followed by stirring at 120 ° C. for 2 hours. Xylene, generated alcohol, excess 2 -Ethylhexanoic acid was distilled off at 180 ° C under normal pressure. To this was added 200 ml of a xylene solution having a bismuth 2-ethylhexanoate concentration of 1.0 mol / l. Thereafter, xylene was added so that the oxide concentration as SrBi ₂ Ta ₂ O _x was 0.2 mol / l. Furthermore, butyl acetate was added to prepare an oxide concentration of 0.1 mol / l as SrBi ₂ Ta ₂ O _x to obtain a main liquid.

The secondary liquid was obtained as follows. To 1000 ml of a xylene solution having a concentration of bismuth 2-ethylhexanoate of 0.1 mol / l, 500 ml of a xylene solution having a concentration of tungsten ethoxide of 0.1 mol / l and 100 g of 2-ethylhexanoic acid were mixed. The mixture was heated to reflux at 120 ° C. for 1 hour under a nitrogen atmosphere, and the solvent was distilled at atmospheric pressure. Xylene was added thereto to prepare an oxide concentration of 0.1 mol / l as Bi ₂ WO ₆ to obtain a secondary liquid.

  The obtained main liquid and secondary liquid were mixed to obtain seven types of mixed liquids having different mixing volume ratios. The mixing volume ratio of the main liquid to the secondary liquid in the mixed liquid was 100: 1, 100: 10, 100: 20, 100: 50, 100: 100, 100: 150, and 100: 200.

  Ferroelectric films were formed from each of these seven types of mixed solutions and solutions containing only the main solution. The film forming method is the same as that in Example 1.

  In Example 3, the same tendency as in Example 1 was observed with respect to Pr.

Example 4
The main liquid was obtained as follows. To 100 ml of 1-methoxy-2-propanol, 37.93 g of lead acetate trihydrate, 19.95 g of zirconium butoxide, and 13.64 g of titanium isopropoxide were added, and the mixture was heated to reflux at 120 ° C. for 1 hour in a nitrogen atmosphere. . Thereafter, 4.5 g of acetylacetone and 1.1 g of water were added, and the solvent was distilled off at normal pressure. This was added to 1-methoxy-2-propanol, the oxide concentration as _{Pb (Zr 0.52 Ti 0.48) O} 3 was prepared so that the 0.3 mol / l, to obtain a main liquid.

On the other hand, the secondary liquid was obtained as follows. 200 ml of a 1-methoxy-2-propanol solution having a germanium ethoxide concentration of 0.5 mol / l was mixed with 250 ml of a 1-methoxy-2-propanol solution having a lead butoxide concentration of 0.5 mol / l. This mixture was heated to reflux at 120 ° C. for 1 hour under a nitrogen atmosphere, and then returned to room temperature. Thereafter, 4.1 g of acetylacetone and 1.0 g of water were added, and the solvent was distilled off at normal pressure. To this, was added 1-methoxy-2-propanol, the oxide concentration as Pb ₅ Ge ₃ O ₁₁ was prepared so as to 0.15 mol / l, to obtain a secondary liquid.

  The obtained main liquid and secondary liquid were mixed to obtain seven types of mixed liquids having different mixing volume ratios. The mixing volume ratio of the main liquid to the secondary liquid in the mixed liquid was 100: 1, 100: 10, 100: 20, 100: 50, 100: 100, 100: 150, and 100: 200.

  Ferroelectric films were formed from each of these seven types of mixed solutions and solutions containing only the main solution. The film forming method is the same as that in Example 1.

  In Example 4, the same tendency as in Example 1 was observed with respect to Pr.

(Experimental example on surface morphology)
Next, the experimental results regarding the surface morphology will be described.

  FIG. 10 is a photomicrograph of a ferroelectric film obtained from the mixed liquid of the main liquid and the secondary liquid according to Example 1. FIG. 11 is a micrograph of a ferroelectric film according to a comparative example.

  Note that the ferroelectric film according to Example 1 in FIG. 10 is a ferroelectric film in which the mixing volume ratio of the main liquid and the sub-liquid is 100: 100. The ferroelectric film according to the comparative example was obtained by forming the main liquid solution shown in Example 1 with the film forming method of Example 1. In both the examples and comparative examples, the thickness of the ferroelectric film was set to 50 nm.

  As shown in FIGS. 10 and 11, it can be seen that the ferroelectric film according to the example has a markedly improved surface morphology than the ferroelectric film according to the comparative example.

  The present invention can be modified in various ways within a range not exceeding the above embodiment.

It is sectional drawing which shows typically the manufacturing process of the ceramic film | membrane using the ceramic raw material liquid which concerns on embodiment. 1 is a cross-sectional view schematically showing a ferroelectric memory device. It is sectional drawing which shows typically the apparatus for forming a raw material body on a base | substrate by LSMCD method. It is a conceptual diagram which shows typically the structure of the raw material body obtained by the apparatus in FIG. It is a conceptual diagram which shows typically the manufacturing process of a 1st multilayer ceramic film. It is a conceptual diagram which shows typically the manufacturing process of a 2nd multilayer ceramic film. It is a conceptual diagram which shows typically the manufacturing process of a 3rd multilayer ceramic film. It is a conceptual diagram which shows typically the manufacturing process of a 4th multilayer ceramic film. It is a flowchart of the film-forming process. 2 is a micrograph of a ferroelectric film obtained from a mixed liquid of a main liquid and a sub liquid according to Example 1. FIG. It is a microscope picture figure of the ferroelectric film which concerns on a comparative example.

Explanation of symbols

10 substrate, 20 raw material body, 30 ceramic film, 42 first crystal, 52 second crystal, 200 apparatus for carrying out LSMCD method, 210 main liquid, 210a first mist, 220 secondary liquid, 220a second Mist, 230,232 sprayer, 240 mesh, 250 mist, 300,400,500 ceramic film

Claims (9)

Of PbZr _y Ti _1-y O ₃ (where 0 <y <1) and Pb _1-x La _x Zr _y Ti _1-y O ₃ (where 0 <x <1, 0 <y <1) A first crystal comprising at least one ferroelectric material of
At least one second crystal and the including ceramic film made of an oxide of one of Pb ₂ MoO ₅ and _Pb 2 VO _5.   The ceramic film according to claim 1, wherein the first crystal and the second crystal are of different types. The oxides are ferroelectric or paraelectric ceramics film according to claim 1 or 2. And the ferroelectric, and the oxide, the molar ratio of 100: 20 to 100: 100 in which the first to third aspects or ceramic film according to an item. A lower electrode;
A ferroelectric film formed above the lower electrode and made of the ceramic film according to any one of claims 1 to 4 ,
And an upper electrode formed above the ferroelectric film. The semiconductor device according to claim 5 , wherein the upper electrode is made of an iridium-based material. A lower electrode;
A piezoelectric body formed above the lower electrode and comprising the ceramic film according to any one of claims 1 to 4 ,
A piezoelectric element comprising an upper electrode formed above the piezoelectric body. The piezoelectric element according to claim 7 , wherein the upper electrode is made of an iridium-based material. An actuator comprising the piezoelectric element according to claim 7 or 8 .