JP2007005028A - Composition for forming bi-based dielectric thin film and bi-based dielectric thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for forming a Bi-based dielectric thin film with which a crystallized thin film of Bi-based dielectric can be obtained even by low-temperature baking below 800°C, and also to provide a Bi-based dielectric thin film. <P>SOLUTION: This composition for forming the Bi-based dielectric thin film is constituted by containing a compound obtained by reaction of alkoxide, organic salt or a complex of at least each metal of Sr, Bi, Ta and a lanthanoid element or a composite metal. The crystallized thin film of the Bi-based dielectric represented by a general formula: Sr<SB>1-X</SB>A<SB>β</SB>Bi<SB>2</SB>+Y(Ta<SB>2-Z</SB>Nb<SB>Z</SB>)O<SB>9+α</SB>... (1) (where A is a lanthanoid element. X, Y, and α are numbers of 0 or more and less than 1 independently, Z is a number of zero or more and less than 2, and β is a number of 0.09 or more and 0.9 or less) is obtained by baking a coating film of this composition at low temperatures below 800°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Bi-based dielectric thin film forming composition and a Bi-based dielectric thin film. Specifically, the present invention relates to a Bi-based dielectric thin film forming composition capable of forming a Bi-based dielectric crystallized thin film by low-temperature firing at less than 800 ° C., and a Bi-based dielectric thin film obtained from the composition. is there.

In recent years, as a material for semiconductor memories and sensors, a crystallized thin film of a dielectric called Bi-based layer-structured ferroelectrics (BLSF) has a low coercive field of PE hysteresis, Various developments have been made since it exhibits excellent characteristics such as polarization inversion in a low electric field. Bi-based layered ferroelectrics are (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ²⁻ (where A is a 1, 2, 3 valent ion or any of these ions) B represents a combination, and B represents a 4, 5, 6-valent ion and a combination of these ions; m = 1 to 5).

  Conventionally, as a material for forming the Bi-based ferroelectric thin film, for example, an alkoxy metal corresponding to a specific metal, a metal complex, a metal acetate, and the like, alcohol, carboxylic anhydride, glycol, β-diketone, dicarboxylic acid An organometallic compound obtained by compounding and hydrolyzing each metal compound constituting a BLSF thin film, or a coating liquid (for example, see Patent Document 1) containing a compound obtained by reacting with a monoester or the like There has been proposed a coating liquid containing, for example, Patent Document 2.

Further, as a device using a BLSF film, a thin film of SrBi ₂ (Ta _x Nb _1-x ) ₂ O ₉ (X = 0 to 1) whose <105> axis is oriented in the thickness direction and a pair sandwiching the thin film There has also been proposed a thin-layer capacitor (see, for example, Patent Document 3), which is characterized by comprising the above electrodes.

Further, it has been confirmed that a thin film of SrBi ₂ Ta ₂ O ₉ based dielectric is excellent in characteristics as BLSF. For example, by introducing lanthanum (La) into a SrBi ₂ Ta ₂ O ₉ dielectric, the characteristics can be further improved, and the ferroelectric is crystallized at a temperature of 1200 ° C. or higher by a solid phase method. Has been announced (Non-patent Document 1).

Japanese Patent No. 3217699 Japanese Patent No. 3108039 Japanese Patent Laid-Open No. 8-23073 62nd Japan Society of Applied Physics Academic Lecture, Proceedings of Lectures, 384-385, 12a-ZR-6, 7

In order to exhibit sufficient characteristics for the Bi-based layered structure ferroelectrics including the aforementioned SrBi ₂ Ta ₂ O _9- based dielectrics, crystallization is necessary, and in order to apply to various circuit devices, Thinning is necessary.

  On the other hand, in the technique described in Non-Patent Document 1, the solid phase method is used for crystallization of the dielectric, but it is difficult to form the dielectric in a thin film by the solid phase method. If the dielectric cannot be thinned, it cannot be applied to a semiconductor circuit substrate such as a semiconductor memory or a semiconductor sensor. In the technique described in Non-Patent Document 1, a calcination temperature of 1200 ° C. is required for crystallization. However, when a temperature exceeding 800 ° C. is applied to a semiconductor circuit substrate, deterioration such as thermal damage is caused. There is a fear.

  Therefore, it is necessary to examine a Bi-based dielectric thin film forming method. Conventionally, Bi-based dielectric thin film forming methods include sputtering, CVD, and coating-type film forming methods. Is provided. Thin film formation methods such as sputtering and CVD have many constituent metal oxide components, which requires expensive equipment and costs, and it is difficult to control and manage the desired dielectric film composition. In particular, application to a large-diameter substrate is considered difficult. On the other hand, the thin film formation method by the coating-type film formation method does not require an expensive apparatus, the film formation cost is relatively low, and the desired dielectric film composition control and management thereof are easy, and therefore promising. Has been.

  However, even when a thin film forming method based on a coating type film forming method, which has many advantages as a thin film forming method, is used, in order to provide the obtained Bi-based dielectric thin film with good electrical characteristics, heating at 800 ° C. or higher is required. Treatment (firing) is necessary, and such heat treatment at a high temperature tends to cause deterioration such as thermal damage to the semiconductor circuit substrate. Therefore, it has been desired that the heat treatment (firing) temperature in the formation process of the Bi-based dielectric thin film is lower than 800 ° C., for example, 700 ° C. or less.

  The present invention has been made in view of such conventional circumstances, and the problem is that a Bi-based dielectric crystallized thin film can be obtained by firing at a low temperature of less than 800 ° C., which is a temperature at which a semiconductor circuit substrate does not undergo thermal degradation. It is an object of the present invention to provide a Bi-based dielectric thin film-forming composition capable of forming a Bi-based dielectric thin film obtained by using the composition.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have obtained a coating-type coating so that a Bi-based dielectric material in which a lanthanoid-based metal element is substituted at the A site of tantalum strontium bismuth (SBT) can be obtained. It has been found that if a coating liquid for forming (composition for forming a Bi-based dielectric thin film) is prepared, a Bi-based dielectric crystallized thin film having excellent characteristics can be formed even by baking at a low temperature of less than 800 ° C. It was.

That is, the Bi-based dielectric thin film forming composition according to the present invention has the following general formula (1):
Sr _1-X AβBi _{2 + Y} (Ta _2−Z Nb _Z ) O ₉₊ α (1)
(In the formula, A represents a lanthanoid element. X, Y and α each independently represents a number of 0 or more and less than 1, Z represents a number of 0 or more and less than 2, and β represents 0.09. And a Bi-based dielectric thin film forming composition for forming a Bi-based dielectric crystallized thin film represented by the formula (1): It contains a compound containing at least Sr, Bi, Ta and a lanthanoid element A obtained by reacting an alkoxide, organic salt or complex of each metal or composite metal of Sr, Bi, Ta and lanthanoid element A And

  The Bi-based dielectric thin film of the present invention is obtained by crystallizing a coating film of the Bi-based dielectric thin film forming composition by firing.

  The composition for forming a Bi-based dielectric thin film of the present invention can be used as a coating solution for obtaining a thin film by a coating-type film forming method, and the coating film can be crystallized by low-temperature baking at 800 ° C. or lower. A dielectric thin film having characteristics suitable for the dielectric film of a circuit device can be formed. Therefore, according to the composition for forming a Bi-based dielectric thin film of the present invention, a Bi-based dielectric crystallized thin film having excellent characteristics can be formed on a semiconductor circuit substrate without causing thermal degradation of the substrate. This can contribute to space saving and high performance of the semiconductor circuit device.

The Bi-based dielectric thin film forming composition of the present invention has the following general formula (1):
Sr _1-X AβBi _{2 + Y} (Ta _2−Z Nb _Z ) O ₉₊ α (1)
(In the formula, A represents a lanthanoid element. X, Y and α each independently represents a number of 0 or more and less than 1, Z represents a number of 0 or more and less than 2, and β represents 0.09. And a Bi-based dielectric thin film forming composition for forming a Bi-based dielectric crystallized thin film represented by the formula (1): It contains a compound containing at least Sr, Bi, Ta and a lanthanoid element A obtained by reacting an alkoxide, organic salt or complex of each metal or composite metal of Sr, Bi, Ta and lanthanoid element A And
In the Bi-based dielectric thin film of the present invention, Nb in the general formula (1) has a composition ratio z of 0 or more and less than 2, so that a composition containing no Nb is possible.

  Examples of the lanthanoid element used in the present invention include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium ( Gd) and the like. Of these, lanthanum is preferred.

Examples of the alcohol that forms the alkoxide of each metal or composite metal of Sr, Bi, Ta, (Nb if necessary) and lanthanoid element A include the following general formula (2)
R ¹ OH (2)
(In the formula, R ¹ represents a saturated or unsaturated hydrocarbon having 1 to 6 carbon atoms.)
The alcohol represented by these is preferable.

  Specific examples of such alcohols include methanol, ethanol, butanol, amyl alcohol, cyclohexanol, methylcyclohexanol, and the like.

Examples of alcohols other than the alcohol include those in which R ¹ is further substituted with an alkoxyl group having 1 to 6 carbon atoms. Specifically, methoxymethanol, methoxyethanol, ethoxymethanol, ethoxyethanol, etc. Is mentioned.

  Examples of the organic salt of each metal or composite metal of Sr, Bi, Ta, (Nb) and lanthanoid element A include acetic acid metal salts, metal alkoxides, β-diketone metal complexes, and the like.

  Specific examples of the metal alkoxide of the lanthanoid element include lanthanum methoxide, lanthanum ethoxide, lanthanum propoxide, lanthanum butoxide, lanthanum ethoxyethylate, and the like.

Examples of the complex of each metal or complex metal of Sr, Bi, Ta, (Nb) and the lanthanoid element A include a β-diketone metal complex. Examples of the β-diketone forming the β-diketone metal complex include the following general formula (3)
R ² COCR ³ HCOR ⁴ (3)
(Wherein, R ² represents a hydrocarbon group represents a saturated or unsaturated having 1 to 6 carbon atoms; R ³ represents H or CH _3; R ⁴ represents an alkyl group or an alkoxyl group having 1 to 6 carbon atoms It is preferable to use at least one selected from β-diketones including β-ketoesters represented by:

  Specific examples of the β-diketone used in the present invention include acetylacetone, 3-methyl-2,4-pentanedione, benzoylacetone and the like. Examples of β-ketoesters include ethyl acetoacetate and diethyl malonate. Complex forming agents other than these are also applicable, but complex forming agents such as dipivaloylmethane and its THF adduct, and hexafluoroacetylacetone that forms a metal halide after calcination are sublimable or volatile. Since it forms a high metal complex, it is not suitable for use in the Bi-based dielectric thin film forming composition of the present invention.

  The Bi-based dielectric thin film forming composition of the present invention is a compound obtained by reacting each metal or composite metal alkoxide, organic salt or complex of the Sr, Bi, Ta, (Nb) and lanthanoid element A Containing.

  Examples of the reaction of the “Sr, Bi, Ta, (Nb) and lanthanoid element A metal alkoxides, organic salts or complexes of lanthanoid elements A” include, for example, water or a hydrolysis reaction using water and a catalyst. Can be mentioned.

  In the hydrolysis reaction, the alkoxide, organic acid or complex of each metal or composite metal of the Sr, Bi, Ta, (Nb) and lanthanoid element A is dissolved in a solvent having an oxygen atom in the molecule, and then Water or water and a catalyst are added, and stirring is performed at 20 to 50 ° C. for several hours to several days.

  Examples of the solvent having an oxygen atom in the molecule include alcohol solvents, polyhydric alcohol solvents, ether solvents, ketone solvents, ester solvents, lower carboxylic acid solvents, and the like.

  Examples of the alcohol solvent include methanol, ethanol, propanol, butanol, amyl alcohol, cyclohexanol, methylcyclohexanol, and the like.

  Examples of the polyhydric alcohol solvent include ethylene glycol monomethyl ether, ethylene glycol monoacetate, diethylene glycol monomethyl ether, diethylene glycol monoacetate, propylene glycol monoethyl ether, propylene glycol monoacetate, dipropylene glycol monoethyl ether, methoxybutanol. Etc.

  Examples of the ether solvent include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane, dioxane and the like.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone, ethyl butyl ketone, trimethylnonanone, acetonitrile acetone, dimethyl oxide, phorone, cyclohexanone, Examples include diacetone alcohol.

  Examples of the ester solvent include ethyl formate, methyl acetate, ethyl acetate, butyl acetate, cyclohexyl acetate, methyl propionate, ethyl butyrate, ethyl oxyisobutyrate, ethyl acetoacetate, ethyl lactate, methoxybutyl acetate, diethyl oxalate, And diethyl malonate.

  Examples of the lower carboxylic acid solvent include acetic acid, propionic acid, butyric acid, valeric acid and the like.

  In the stabilization treatment to be described later, these solvents, particularly alcohol solvents, react with the respective metals or complex metal alkoxides, organic salts or complexes of the Sr, Bi, Ta, (Nb), and lanthanoid elements A. Some may have been done.

  The said solvent can be used individually or in the form of mixing 2 or more types.

  In addition, each metal alkoxide, organic salt or complex of Sr, Bi, Ta, and (Nb) shows good solubility in aromatic hydrocarbon solvents, but these solvents are used and controlled. The method and the like tend to be remarkably limited, which is not preferable.

  As the various solvents described above, the most preferable solvents can be used depending on the application conditions such as the open spin coating method, the closed spin coating method, the LSM-CVD method of mist coating, and the dipping method.

  Examples of the catalyst used in the present invention include those known for metal alkoxide hydrolysis reactions, such as inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, acid catalysts such as organic acids such as acetic acid, propionic acid and butyric acid, and water. Examples thereof include inorganic and organic alkali catalysts such as sodium oxide, potassium hydroxide, ammonia, monoethanolamine, diethanolamine, and tetramethylammonium hydroxide.

  Here, when an inorganic alkali such as sodium hydroxide or potassium hydroxide is used, metal ions such as sodium and potassium remain in the Bi-based dielectric thin film forming composition and affect the electrical characteristics of the coating. There are concerns. In addition, when nitrogen-containing alkalis such as ammonia and amines are used, nitrogen compounds with a high boiling point may be formed after the hydrolysis reaction, which may affect the densification of the coating during the firing process. Concerned. Therefore, in the present invention, it is particularly preferable to use an acid catalyst.

  In the hydrolysis reaction, a solution of each metal of Sr, Bi, Ta, (Nb) and lanthanoid element A or an alkoxide of a composite metal, an organic salt or a complex having an oxygen atom in the molecule is dissolved on the electrode. After coating, it can also be carried out by exposing the coating surface to a humidified atmosphere. Specifically, for example, it can be performed at 50 to 120 ° C. for about 10 to 60 minutes under a humidity of 50 to 100%.

  The above conditions can be appropriately selected according to the use of the coating, and are not limited to the above.

  By performing the hydrolysis treatment in this manner, the content of the organic component in the entire coating film after the drying step can be reduced. Moreover, since the metalloxane bond of each metal is formed, precipitation (segregation) and burning of metal elements such as Bi can be suppressed. This is because each organometallic compound has an organic group in its structure, but by hydrolyzing, an organic group such as an alkoxyl group can be eliminated to form a more inorganic metalloxane bond. The detached organic group becomes a low-boiling point alcohol, glycol or the like and remains in the Bi-based dielectric thin film forming composition or film, but evaporates with the solvent in the drying process. Therefore, a dense film can be formed.

  In addition, the formation of metalloxane bonds strengthens the bond between metal elements, suppresses the precipitation (segregation) and burnout of metal elements such as Bi, and forms a film with low leakage current and excellent resistance to hydrogen heat treatment and pressure resistance. Is possible.

By calcining the compound obtained by the hydrolysis at less than 800 ° C., preferably at 750 ° C. or less, more preferably at 700 ° C. or less, the following general formula (1)
Sr _1-X AβBi _{2 + Y} (Ta _2−Z Nb _Z ) O ₉₊ α (1)
(In the formula, A represents a lanthanoid element. X, Y and α each independently represents a number of 0 or more and less than 1, Z represents a number of 0 or more and less than 2, and β represents 0.09. A Bi-based dielectric crystallized thin film represented by the following formula can be obtained.

  The lanthanoid element A is preferably a lanthanum (La) element. This is because it is particularly effective for lowering the firing temperature.

  In the general formula (1), x represents a number of 0 or more and less than 1, y represents a number of 0 or more and less than 1, z represents a number of 0 or more and less than 2, and α represents 0 or more and 1 or less. Represents a number less than.

  Β represents a number of 0.09 or more and 0.9 or less, and preferably in the range of 0.18 or more and 0.45 or less. By setting it to 0.09 or more and 0.9 or less, it is particularly effective for lowering the firing temperature.

  The “compound obtained by the reaction such as hydrolysis” contained in the composition for forming a Bi-based dielectric thin film of the present invention is a compound obtained by reacting the metal alkoxide with a stabilizer. There may be. The “compound” may alternatively be a compound obtained by hydrolyzing the metal alkoxide with water or water and a catalyst and then reacting with a stabilizer.

  The stabilizer is for improving the storage stability of the Bi-based dielectric thin film forming composition. In the present invention, the stabilizer is a carboxylic acid anhydride, a dicarboxylic acid monoester, a β-diketone, or a glycol. At least one selected from among these is preferably used.

Examples of the carboxylic anhydrides include the following general formula (4)
R ⁵ (CO) ₂ O (4)
(In the formula, R ⁵ represents a divalent saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms.) At least one selected from carboxylic anhydrides represented by the formula is preferably used. Specific examples of the carboxylic anhydrides include maleic anhydride, citraconic anhydride, itaconic anhydride, succinic anhydride, methyl succinic anhydride, glutaric anhydride, α-methylglutaric anhydride, α, α-dimethyl glutaric acid, trimethyl succinic anhydride, and the like can be mentioned.

Examples of the dicarboxylic acid monoesters include the following general formula (5)
R ⁶ OCOR ⁷ COOH (5)
(In the formula, R ⁶ represents a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms; R ⁷ represents a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms.) Preferably, at least one selected from dicarboxylic acid monoesters represented by the formula:

  As the dicarboxylic acid monoesters used in the present invention, specifically, for example, those obtained by reacting a dibasic carboxylic acid with an alcohol to form a half ester can be used. Specifically, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelic acid, sebacic acid, maleic acid, citraconic acid, itaconic acid, methyl succinic acid, α-methyl glutaric acid, At least one dicarboxylic acid such as α, α-dimethylglutaric acid or trimethylglutaric acid, and methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, ethylene glycol monomethyl ether, propylene glycol It can be synthesized by an esterification reaction with at least one kind such as monomethyl ether by a known method.

  As the β-diketone, at least one selected from β-diketones including a β-ketoester represented by the general formula (3) is preferably used.

  Specific examples of the β-diketone used in the present invention include acetylacetone, 3-methyl-2, 4-pentanedione, benzoylacetone and the like. Examples of the β-ketoester used in the present invention include ethyl acetoacetate and diethyl malonate. Complex forming agents other than these are also applicable, but complex forming agents such as dipivaloylmethane and its THF adduct, and hexafluoroacetylacetone that forms a metal halide after calcination are sublimable or volatile. Use in the composition of the present invention is not preferred because it forms a high metal complex.

As the glycols, the following general formula (6)
HOR ⁸ OH (6)
(In the formula, R ⁸ represents a divalent saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms.) At least one selected from glycols represented by

  Specific examples of the glycols used in the present invention include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexylene glycol, and glycerin glycol. These glycols are particularly effective when β-diketone is used as a stabilizer, and increases the stability of the liquid after the subsequent hydrolysis reaction.

  Any of the above stabilizers is preferably a short chain having 1 to 6 carbon atoms from the viewpoint of enhancing the inorganic properties of the coating after the drying step.

  A reaction product of the reaction product of each metal of the Sr, Bi, Ta, (Nb), and the lanthanoid element A or an alkoxide, organic salt or complex of a complex metal and the stabilizer is also suitable in the present invention. Can be used for

  Specific examples of the reaction when the stabilizer is used include the following, but are not limited thereto.

  [1] Reaction between metal alkoxide and dicarboxylic acid monoester, [2] Reaction between metal alkoxide and carboxylic anhydride, [3] Reaction between metal alkoxide and β-ketoester, [4] Heterogeneous reaction of [1] Reaction between products, [5] Reaction between metal alkoxide, dicarboxylic acid monoester and β-ketoester, [6] Reaction between metal alkoxide, carboxylic anhydride and β-ketoester, [7] Metal alkoxide and metal acetate [8] reaction of the reaction product of [7] with a dicarboxylic acid monoester, carboxylic anhydride or β-ketoester, [9] reaction generation of [7] [10] a partial hydrolyzate of the reaction product of [8], [11] an acidic metal alkoxide and a basic alkoxide. Reaction with metal, [12] Reaction of reaction product of [11] with dicarboxylic acid monoester, carboxylic anhydride or β-ketoester, [13] Reaction of different metals with reaction products of [12] [14] A partial hydrolyzate of the reaction product of [13].

  [1] to [6], [8], [9], [12] and [13] are suitable as a MOD (Metallo-Organic Decomposition) type coating solution, and [10] and [14] are sol- Suitable for gel-type coating liquid. The compounds [7] and [11] are obtained by substituting a part of the alkoxy groups with carboxylic anhydride, β-diketone, etc., thereby stabilizing the storage of the Bi-based dielectric thin film forming composition, and practical organic The solubility with respect to a solvent can be improved.

  The Bi-based dielectric thin film forming composition containing the compound obtained by the hydrolysis reaction may be used as it is, or further diluted with a solvent having the oxygen atom in the molecule. Also good.

  As described above, the Bi-based dielectric thin film of the present invention is obtained by crystallizing a coating film of the Bi-based dielectric thin film forming composition by firing.

  Hereinafter, an example of a Bi-based dielectric thin film obtained by using the Bi-based dielectric thin film forming composition of the present invention and an example of a manufacturing method when this thin film is applied to a dielectric memory as a semiconductor circuit device will be described.

  First, a substrate such as a Si wafer is oxidized to form a Si oxide film on the substrate, and a metal such as Pt, Ir, Ru, Re, Os, and a conductive metal oxide that is a metal oxide thereof are formed thereon. The lower electrode is formed by a known method such as sputtering or vapor deposition.

  Next, the Bi-based dielectric thin film forming composition of the present invention is applied onto the lower electrode by a known application method such as a spinner method or a dip method, followed by drying at a temperature of 50 to 200 ° C., Temporary baking is performed at a temperature of 200 to 700 ° C. Preferably, the operation from application to pre-baking is repeated several times to set the desired film thickness.

  Next, main firing is performed in an oxygen atmosphere at a temperature of less than 800 ° C., preferably 750 ° C. or less, more preferably 700 ° C. or less to form a Bi-based dielectric crystallized thin film. In the main baking step, a furnace method in which the temperature is raised from room temperature to the main baking temperature at a temperature increase rate of about 5 to 20 ° C./min, and then maintained at the main baking temperature for about 30 to 80 minutes, from room temperature to 50 Various firing methods can be selected such as RTP method in which the temperature is raised to the main firing temperature at a temperature rise rate of about 150 ° C./sec, and then the main firing temperature is maintained for about 0.5 to 3 minutes. .

  Next, an electrode (upper electrode) is formed on the dielectric thin film produced as described above. As the upper electrode, metals, metal oxides and the like as the material for the lower electrode can be used, and these materials are formed on a dielectric thin film by a known method such as sputtering or vapor deposition to form a dielectric memory. obtain. At this time, as the upper electrode, a material different from that of the lower electrode may be used. For example, Ir may be used for the lower electrode and Ru may be used for the upper electrode.

  In addition, when performing a hydrolysis reaction in a humidified atmosphere, it can be carried out at a humidity of 50 to 100%, preferably 70 to 100%, a temperature of 50 to 120 ° C., for 10 to 60 minutes before the above-described preliminary baking. .

After the upper electrode is formed, a protective film such as SiO _{2 is} formed (passivation), aluminum wiring, and the like are performed. Since the Bi-based dielectric thin film of the present invention is particularly excellent in resistance to hydrogen heat treatment, there is no risk of deterioration of dielectric characteristics during the formation of the passivation film and during the firing of the aluminum wiring, and the dielectric memory obtained is Electrical characteristics can be realized satisfactorily.

  Further, even if it is a Bi-based dielectric thin film forming composition that is not sufficiently mineralized by the sol-gel method (hydrolysis treatment) or a Bi-based dielectric thin film forming composition that is not hydrolyzed at all. When the film is formed on the substrate, the film can be mineralized by hydrolytic condensation polymerization by exposing the film to a humidified atmosphere for a certain period of time before firing the film, and a dense film can be formed. is there.

  If the hydrolysis treatment in the Bi-based dielectric thin film forming composition described above is excessively performed, the Bi-based dielectric thin film-forming composition may cause thickening / gelation or change with time, A method using the hydrolysis treatment at the time of forming the film is also effective.

  EXAMPLES Hereinafter, examples of the present invention will be shown and the present invention will be described in more detail. However, the present invention is not limited to the following examples. In addition, about the reagent etc. which were used except what was described especially, what was marketed generally was used.

Example 1
2 moles of tantalum ethoxide, 2.1 moles of bismuth butoxide, 0.72 moles of strontium isopropoxide and 0.18 moles of lanthanum ethoxyethylate are stirred in propylene glycol monomethyl ether for 10 minutes at room temperature to obtain a uniform mixed solution It was. Next, 3 mol of ethyl acetoacetate was added, and the mixture was heated and stirred at 60 ° C. for 2 hours. Thereafter, 1 mol of propylene glycol was added and stirred at room temperature for 1 hour. Furthermore, 2 mol of water was added dropwise with stirring, and after completion of the total addition, the mixture was stirred at room temperature for 2 hours. As described above, a Bi-based dielectric thin film forming composition having a metal oxide solid content of 6.5% by mass was obtained.

  The Bi-based dielectric thin film forming composition thus obtained was spin-coated on a Si substrate at 500 rpm for 1 second and then at 2000 rpm for 30 seconds using a spin coater to obtain a coating film having a uniform thickness. Thereafter, the first heat treatment was performed at 600 ° C. for 30 minutes in a furnace. After repeating the above coating to heat treatment three times, the second heat treatment was performed at 600 ° C. for 1 hour in the furnace. As a result, a dielectric thin film 1 of about 100 nm was obtained.

[X-ray diffraction (XRD) measurement]
XRD measurement was performed on the obtained dielectric thin film 1. Here, FIG. 1 is a diagram showing a graph (XRD curve) obtained by XRD measurement of the dielectric thin film 1. From FIG. 1, the peak of (115), which is the main axis of the SBTN dielectric thin film, was developed by low-temperature firing at 600 ° C., and it was confirmed that the dielectric thin film was crystallized. For the X-ray diffraction, a measuring apparatus “RINT-2500HF” (apparatus name; manufactured by Rigaku Corporation) was used. The measurement was performed under the measurement conditions of X-ray: CuKα ₁ , tube voltage: 30 kV, tube current: 50 mA, scan speed: 20 ° / min, scan step: 0.020 °.

[Scanning electron microscope (SEM) observation]
When the obtained crystallized dielectric thin film was observed with a scanning electron microscope (SEM), it was confirmed that grains (grain boundaries) accompanying crystallization were formed.

(Example 2)
A dielectric thin film 2 was obtained in the same manner as in Example 1 except that the amount was changed to 0.63 mol of strontium isopropoxide and 0.27 mol of lanthanum ethoxyethylate. The dielectric thin film 2 was subjected to XRD measurement in the same manner as in Example 1. Here, FIG. 2 is a diagram showing a graph (XRD curve) obtained by XRD measurement of the dielectric thin film 2. From FIG. 2, the peak of (115), which is the main axis of the SBTN dielectric thin film, was developed by firing at a low temperature of 600 ° C., and it was confirmed that the dielectric thin film was crystallized. Further, when the obtained crystallized dielectric thin film was observed with a scanning electron microscope (SEM), it was confirmed that grains (grain boundaries) accompanying crystallization were formed.

(Example 3)
A dielectric thin film 3 was obtained in the same manner as in Example 1 except that the amount was changed to 0.45 mol of strontium isopropoxide and 0.45 mol of lanthanum ethoxyethylate. The dielectric thin film 3 was subjected to XRD measurement in the same manner as in Example 1. Here, FIG. 3 is a diagram showing a graph (XRD curve) obtained by XRD measurement of the dielectric thin film 3. From FIG. 3, the peak of (115), which is the main axis of the SBTN dielectric thin film, was developed by firing at a low temperature of 600 ° C., and it was confirmed that the dielectric thin film was crystallized. Moreover, when the obtained crystallized film was observed with the scanning electron microscope (SEM), it was confirmed that the grain (grain boundary) accompanying crystallization was formed.

(Comparative example)
Dielectric thin film 4 was obtained in the same manner as in Example 1 except that strontium isopropoxide was changed to 0.9 mol and lanthanum ethoxyethylate was not blended. The dielectric thin film 4 was subjected to XRD measurement in the same manner as in Example 1. Here, FIG. 4 is a diagram showing a graph (XRD curve) obtained by XRD measurement of the dielectric thin film 4. From FIG. 4, the peak of (115), which is the main axis of the SBTN dielectric thin film, is not expressed at a low temperature firing of 600 ° C., but instead a broad peak is expressed by the precursor fluorite. It was confirmed that the dielectric thin film was not crystallized. Moreover, when the obtained dielectric thin film was observed with the scanning electron microscope (SEM), it was confirmed that the generation | occurrence | production ratio of the grain (grain boundary) accompanying crystallization is small.

  As described above, the Bi-based dielectric thin film forming composition of the present invention can be used as a coating solution for obtaining a thin film by a coating type film forming method, and the coating film is fired at a low temperature of 800 ° C. or lower. Thus, a dielectric thin film having characteristics suitable for a dielectric film of a semiconductor circuit device can be formed. Therefore, according to the composition for forming a Bi-based dielectric thin film of the present invention, it is possible to form a crystallized thin film on a Bi-based dielectric having excellent characteristics without causing thermal degradation of the substrate on the semiconductor circuit substrate. This can contribute to space saving and high performance of the semiconductor circuit device.

It is a figure which shows the XRD curve of the dielectric thin film 1 obtained in Example 1. FIG. It is a figure which shows the XRD curve of the dielectric thin film 2 obtained in Example 2. FIG. It is a figure which shows the XRD curve of the dielectric thin film 3 obtained in Example 3. FIG. It is a figure which shows the XRD curve of the dielectric thin film 4 obtained in the comparative example.

Claims (8)

The following general formula (1)
Sr _1-X AβBi _{2 + Y} (Ta _2−Z Nb _Z ) O ₉₊ α (1)
(In the formula, A represents a lanthanoid element. X, Y and α each independently represents a number of 0 or more and less than 1, Z represents a number of 0 or more and less than 2, and β represents 0.09. A Bi-based dielectric thin film forming composition for forming a Bi-based dielectric crystallized thin film represented by the following formula:
Sr, Bi, Ta, and a lanthanoid element A obtained by reacting at least each metal of Sr, Bi, Ta, and a lanthanoid element A in the general formula (1), or an alkoxide, organic salt, or complex of a complex metal A composition for forming a Bi-based dielectric thin film, comprising a compound containing at least.   The composition for forming a Bi-based dielectric thin film according to claim 1, wherein the coating film can be crystallized by low-temperature firing at less than 800 ° C.   3. The Bi-based dielectric thin film forming composition according to claim 1, wherein the Bi-based dielectric crystallized thin film is a dielectric thin film formed on a semiconductor circuit substrate.   The composition for forming a Bi-based dielectric thin film according to any one of claims 1 to 3, wherein the lanthanoid-based element A is lanthanum (La).   A Bi-based dielectric thin film obtained by crystallizing a coating film of the composition for forming a Bi-based dielectric thin film according to any one of claims 1 to 4 by firing.   The Bi-based dielectric thin film according to claim 5, wherein the firing temperature is less than 800 ° C.   The Bi-based dielectric thin film according to claim 5 or 6, which is a crystalline dielectric thin film formed on a semiconductor circuit substrate.   The Bi-based dielectric thin film according to claim 7, wherein the semiconductor circuit board is a circuit board for a dielectric memory.

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