JP3751617B2 - Method for forming ferroelectric film - Google Patents

Description

  The present invention relates to a method for forming a ferroelectric film having a bismuth layer structure, and more particularly, to a method for forming a ferroelectric film having a bismuth layer structure using a metal organic chemical vapor deposition method.

  In recent years, with the advancement of digital technology, electronic devices have become more sophisticated as the tendency to process and store large amounts of data has been promoted, and the integration of semiconductor integrated circuit devices used in electronic devices has increased. The miniaturization of semiconductor elements is progressing rapidly.

  In order to realize high integration of dynamic RAM (Random Access Memory), a dielectric having a high dielectric constant (hereinafter referred to as a high dielectric) is used instead of the conventional silicon oxide or silicon nitride. A technology used as a capacitor film of an element has been widely researched and developed.

  Furthermore, with the aim of commercializing a nonvolatile RAM that can operate at a lower voltage and can be written and read at a higher speed than before, research on FeRAM (Ferroelectric Random Access Memory) using a ferroelectric film having spontaneous polarization characteristics Development is actively underway.

  As a ferroelectric film used for a nonvolatile RAM, a ferroelectric film having a bismuth layer structure that is excellent in rewriting resistance and capable of low voltage operation is promising. In general, a bismuth layer structure is represented by the following chemical formula.

(Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2-
(However, m is an integer of 1 or more, A is a monovalent, divalent or trivalent metal, and B is a tetravalent, pentavalent or hexavalent metal.)

Among a group of materials having a bismuth layer structure, SrBi ₂ Ta ₂ O ₉ (commonly known as SBT), SrBi ₂ Nb ₂ O ₉ (commonly known as SBN), SrBi ₂ (Ta _1-x Nb _x ) ₂ O ₉ ( However, materials such as 0 <X <1, commonly known as SBTN) are often used.

In this bismuth layered structure, bismuth oxide layers (Bi ₂ O ₂ ) and pseudo-perovskite layers (A _m-1 B _m O _{3m + 1} ) are alternately stacked.

  Since a ferroelectric film having a bismuth layer structure is usually composed of three or more kinds of metals, the composition ratio in the ferroelectric film must be accurately controlled in order to develop good ferroelectric characteristics. is necessary.

  Ferroelectric film formation methods are roughly classified into CSD (Chemical Solution Deposition) and vapor phase growth.

  The CSD method is a method of forming a predetermined film by directly applying a solution to a substrate and performing a heat treatment. The CSD method is a MOD (Metal Organic Decomposition) method (organic metal pyrolysis method) according to the type of solution. Or there is a sol-gel method. In addition to the spin coating method that is usually used, there is an LSMCD (Liquid Source Misted Chemical Deposition) method in which the solution is applied in the form of a mist in addition to the spin coating method that is usually used.

  On the other hand, the vapor phase growth method includes a sputtering method, a MOCVD (Metal Organic Chemical Vapor Deposition) method (organic metal vapor phase growth method) and the like.

  As described above, there are various film forming methods as a method for forming the ferroelectric film. Conventionally, the CSD method has been generally used. When the ferroelectric film is formed by the CSD method, the metal composition ratio in the solution is almost the same as the metal composition ratio in the finally formed ferroelectric film. Can be easily controlled. Therefore, the CSD method is a suitable method for controlling the composition ratio in a ferroelectric film having a bismuth layer structure containing three or more kinds of metals.

  By the way, in order to realize high integration of the ferroelectric memory device, it is necessary to form a three-dimensional capacitor in the future. However, in the three-dimensional capacitor, the ferroelectric film seems to have good step coverage. It is required to form a film. In this regard, it is difficult to form a ferroelectric film having good step coverage by using the CSD method, but a ferroelectric film having good step coverage is formed by using a vapor phase growth method. A possible MOCVD method is expected.

  In the MOCVD method, a liquid-phase or solid-phase organometallic compound is vaporized by heating, the vaporized organometallic compound is transported onto the substrate, and then the organometallic compound vaporized on the substrate held at a high temperature is removed. In this method, metal or metal oxide is deposited by thermal decomposition. When forming a binary system or more material such as a ferroelectric film, an organic compound containing a metal constituting the ferroelectric film is prepared as a supply source, and the gas supply amount introduced into the chamber is individually controlled. Thus, a method of forming a ferroelectric film having a desired composition ratio is common.

  However, when a ferroelectric film having a desired composition ratio is formed by the MOCVD method by individually controlling the gas supply amount as described above, the composition ratio in the ferroelectric film can be easily controlled. The deposition of the film is governed by supply rate control (a state in which the deposition rate is not based on the substrate temperature but depends on the gas supply rate). For this reason, even if the MOCVD method capable of forming a ferroelectric film having excellent step coverage is used, when a ferroelectric film is formed on a substrate having a deep step, the amount of gas supply is large. On the other hand, the deposition rate is high in the convex portion, while the deposition rate is slow in the concave portion where the gas supply amount is small, so that the step coverage of the ferroelectric film deposited on the substrate is deteriorated.

  By the way, in order to improve the step coverage of the ferroelectric film, the substrate temperature is lowered to deposit the ferroelectric film at a reaction rate-determined condition (deposition rate depends on the substrate temperature rather than the gas supply amount). You can do it. However, in the case where the ferroelectric film is deposited at a reaction rate, it is difficult to control the composition ratio in the ferroelectric film.

  In order to change the composition ratio in the ferroelectric film, it is only necessary to change the deposition rate ratio of each metal constituting the ferroelectric film by changing parameters such as the substrate temperature, pressure or oxygen partial pressure. However, since the deposition rate of each metal changes uniformly, fine adjustment of the deposition rate ratio of each metal is possible, but the deposition rate ratio of each metal cannot be changed greatly.

  In order to greatly change the deposition rate ratio, it is necessary to change the type of organic group in each organometallic compound including the metal constituting the ferroelectric film.

  However, since organic metal compounds require many conditions such as vaporization at low temperature, no thermal decomposition during transportation, and decomposition at an appropriate rate on the substrate, the type of organic group is selected. However, since the materials are limited, there is a problem that it is difficult to easily obtain an organometallic compound made of an appropriate material.

  In view of the foregoing, as a conventional method of forming a first ferroelectric film, there is a method of forming a ferroelectric film having a bismuth layer structure using double alkoxide (see, for example, Patent Document 1).

According to the conventional method for forming a first ferroelectric film, the metal corresponding to A and B represented by (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- is included. By using a metal alkoxide compound, the number of raw material gases that have been required up to three can be reduced to at least two, so that the composition ratio in the ferroelectric film can be easily controlled.

  Recently, in order to realize a megabit-class highly integrated memory device in a ferroelectric memory device, a stack type memory cell is used in the ferroelectric memory device instead of a conventional planar memory cell. When using a stack type memory cell, the contact surface between the contact plug and the lower electrode of the capacitor element is oxidized by high-temperature heat treatment in an oxygen atmosphere necessary for crystallizing the ferroelectric film. Become. Therefore, generally, an oxygen barrier film such as iridium oxide is formed between the contact plug and the lower electrode.

  However, since the oxygen barrier film has a heat resistance limit, it is required that the heating temperature for crystallizing the ferroelectric film by heat treatment be low. According to the first conventional method for forming a ferroelectric film, a method for forming a ferroelectric film having excellent step coverage and a desired composition ratio can be provided. However, a metal alkoxide is used. Thus, it is necessary to crystallize the ferroelectric film by a heat treatment at a high temperature, as in the usual method for forming the ferroelectric film. Thus, in the conventional first method for forming a ferroelectric film, the heat treatment for crystallizing the ferroelectric film cannot be performed at a low temperature.

On the other hand, a conventional second method for forming a ferroelectric film is disclosed as a method for performing heat treatment at the time of crystallizing a ferroelectric film at a low temperature (see, for example, Patent Document 2). A conventional second method for forming a ferroelectric film is to combine Bi shown in the above (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ²⁻ and metals corresponding to A and B. In this method, a ferroelectric film is formed by a CSD method using a triple alkoxide solution. According to the conventional second method for forming a ferroelectric film, since a triple alkoxide solution having the same atomic arrangement as the final crystal structure of the ferroelectric film is already used in the molecule, the ferroelectric film is crystallized. Since the activation energy required for this is reduced, the heat treatment for the ferroelectric film can be performed at a low temperature.

Japanese Patent No. 3116768 Japanese Patent Laid-Open No. 11-80181

  As described above, the conventional second method for forming a ferroelectric film is a method for forming a ferroelectric film by a CSD method using a triple alkoxide solution as a raw material. Therefore, according to the method of forming a ferroelectric film by MOCVD using a triple alkoxide solution as a raw material, a ferroelectric film having excellent step coverage and realizing a desired composition ratio can be formed. When the ferroelectric film is crystallized, it is naturally expected that the ferroelectric film can be heat-treated at a low temperature.

  However, since triple alkoxide contains a total of five three types of metal elements in one molecule, the molecular weight inevitably increases. For this reason, in order to obtain the vapor pressure required when forming a ferroelectric film, it is necessary to heat the triple alkoxide solution at a high temperature. However, when the triple alkoxide solution is heated at a high temperature, the triple alkoxide is thermally decomposed. Resulting in. Therefore, when forming a ferroelectric film using the MOCVD method, it is impossible to use a triple alkoxide solution as a raw material.

  In view of the foregoing, an object of the present invention is to form a ferroelectric film having a bismuth layer structure by performing a heat treatment at a low temperature on a ferroelectric film formed by the MOCVD method.

In order to solve the above-described problem, the first ferroelectric film forming method according to the present invention includes at least A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] in the chamber. ₂ (where A is a divalent metal or a metal compound containing a divalent metal in an arbitrary ratio, R ¹ , R ² , R ³ and R ⁴ are the same or different, and C and H are A first source gas composed of a first organometallic compound represented by: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) (provided that B is a metal compound containing pentavalent metal or pentavalent metal in an arbitrary ratio, and R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different and contain C and H A second source gas composed of a second organometallic compound represented by the following formula: and an oxidizing gas, and a step of forming a film by a metal organic chemical vapor deposition method. And features.

According to the first ferroelectric film formation method, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ And a first organometallic compound represented by the formula: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) As a result of the chemical reaction with the second organometallic compound represented by the formula, a partial structure included in the crystal structure of the ferroelectric film having a bismuth layer structure to be finally formed is formed. Since the activation energy required when forming a ferroelectric film having a layered structure is reduced, a ferroelectric film having a bismuth layered structure can be formed by crystallization by heat treatment at a low temperature.

In the second ferroelectric film forming method according to the present invention, at least A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ is formed in the chamber. ) ₂ (where A is a divalent metal or a metal compound containing a divalent metal in an arbitrary ratio, and R ¹ , R ² , R ³ and R ⁴ are the same or different, and C and H R ²¹ , R ²² and R ²³ are the same or different, and are hydrogen groups or organic groups containing C and H.) First source gas and B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) (where B is a metal compound containing pentavalent metal or pentavalent metal in an arbitrary ratio) R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different, and are organic groups containing C and H.) 2 raw materials And a step of forming a film by a metal organic chemical vapor deposition method.

According to the method for forming the second ferroelectric film, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ And a first organometallic compound represented by the formula: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) As a result of the chemical reaction with the second organometallic compound represented by the formula, a partial structure included in the crystal structure of the ferroelectric film having a bismuth layer structure to be finally formed is formed. Since the activation energy required when forming a ferroelectric film having a layered structure is reduced, a ferroelectric film having a bismuth layered structure can be formed by crystallization by heat treatment at a low temperature. Furthermore, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ In the first organometallic compound represented by the formula (1), since two amines are coordinated to the metal element A, the metal element A is electrically shielded and the intermolecular force is reduced. Since the organometallic compound can obtain a low vaporization temperature for use in an actual process, the process margin can be increased.

The ferroelectric film formed by the first and second ferroelectric film forming methods of the present invention is preferably represented by (Bi ₂ O ₂ ) ²⁺ (AB ₂ O ₇ ) ²⁻ .

  In the first and second ferroelectric film forming methods of the present invention, it is preferable to further include a step of introducing water vapor into the chamber.

  In this way, molecules after the reaction formed by the chemical reaction between the first organometallic compound and the second organometallic compound further undergo a polycondensation reaction to form a polymer network of metal and oxygen. Therefore, a ferroelectric film having a bismuth layer structure can be formed by crystallization by heat treatment at a lower temperature.

According to the first method of forming a ferroelectric film according to the present invention, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ And a first organometallic compound represented by the formula: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) As a result of the chemical reaction with the second organometallic compound represented by the formula, a partial structure included in the crystal structure of the ferroelectric film having a bismuth layer structure to be finally formed is formed. Since the activation energy required when forming a ferroelectric film having a layered structure is reduced, a ferroelectric film having a bismuth layered structure can be formed by crystallization by heat treatment at a low temperature.

Further, according to the second method for forming a ferroelectric film of the present invention, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ And a first organometallic compound represented by the formula: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) As a result of the chemical reaction with the second organometallic compound represented by the formula, a partial structure included in the crystal structure of the ferroelectric film having a bismuth layer structure to be finally formed is formed. Since the activation energy required when forming a ferroelectric film having a layered structure is reduced, a ferroelectric film having a bismuth layered structure can be formed by crystallization by heat treatment at a low temperature. Furthermore, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ In the first organometallic compound represented by the formula (1), since two amines are coordinated to the metal element A, the metal element A is electrically shielded and the intermolecular force is reduced. Since the organometallic compound can obtain a low vaporization temperature for use in an actual process, the process margin can be increased.

In the following embodiments, in the general formula (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ²⁻ , a bismuth layered structure represented by the following general formula when m = 2 is used. A case of forming a ferroelectric film having the above will be described.

(Bi ₂ O ₂ ) ²⁺ (AB ₂ O ₇ ) ^2-
(However, A is a metal compound containing a divalent metal or a divalent metal in an arbitrary ratio, and B is a metal compound containing a pentavalent metal or a pentavalent metal in an arbitrary ratio.)

  A is, for example, Ca, Sr or Ba, and B is, for example, V, Nb or Ta.

  FIG. 1 shows a cross-sectional structure of a capacitive element having a ferroelectric film formed by the method of forming a ferroelectric film according to each embodiment of the present invention, taking the case where the capacitive element is a three-dimensional capacitive element as an example. The description will be given with reference.

  As shown in FIG. 1, an impurity diffusion layer 2 serving as a source region or a drain region is formed on a surface portion of a semiconductor substrate 1, and a gate electrode 3 is formed on the semiconductor substrate 1 via a gate insulating film. A field effect transistor 4 is formed by the impurity diffusion layer 2 and the gate electrode 3.

  A protective insulating film 5 is deposited on the semiconductor substrate 1 so as to cover the field effect transistor 4, and a contact plug 6 made of tungsten having a lower end connected to the impurity diffusion layer 2 is formed on the protective insulating film 5. Embedded.

  An interlayer insulating film 8 having a concave opening 7 exposing the upper end of the contact plug 6 is formed on the protective insulating film 5, and the lower surface of the concave opening 7 is the upper end of the contact plug 6. An oxygen barrier film 9 made of iridium oxide is formed. The concave opening 7 has a strong bismuth layer structure deposited on the oxygen barrier film 9 in order from the bottom by the first electrode 10 and the ferroelectric film forming method according to each embodiment. A capacitor insulating film made of the dielectric film 11 and the second electrode 12 are formed.

  The ferroelectric film formed by the method for forming a ferroelectric film according to the present invention is not limited to the one used only for the capacitive element having the above-described structure, and the three-dimensional capacitive element It is not limited to.

(First embodiment)
A method for forming a ferroelectric film according to the first embodiment of the present invention will be described below with reference to FIGS.

  In the first embodiment, a first source gas made of the first organometallic compound, a second source gas made of the second organometallic compound, and an oxidizing gas are introduced into the chamber, and the MOCVD method is used. Then, a ferroelectric film 11a (not shown) is formed on the first electrode 10, and the ferroelectric film 11a is subjected to a heat treatment to be crystallized, whereby a ferroelectric having a bismuth layer structure is formed. The body film 11 is formed. In the MOCVD method, a ferroelectric film 11a is formed on the first electrode 10 by causing a chemical reaction between the first source gas, the second source gas, and the oxidizing gas at a predetermined substrate temperature. It is a method to form a film.

  First, the first source gas used in the method for forming a ferroelectric film according to the first embodiment of the present invention will be described. The first source gas is composed of a first organometallic compound containing bismuth and a metal element A represented by the following general formula (1).

A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (1)

Here, A is a metal compound containing a divalent metal or a divalent metal in an arbitrary ratio, and R ¹ , R ² , R ³ and R ⁴ are the same or different and contain C and H And an organic group in which O or N may be added together or O or N may not be added.

  The molecular structure of the first organometallic compound will be described with reference to FIG. In FIG. 2, a solid line indicates an ionic bond or a covalent bond, and a broken line indicates a coordinate bond. In practice, it is difficult to distinguish between coordination bonds and other bonds.

As shown in FIG. 2, the metal element A has a structure sandwiched between oxygen and bismuth. Surrounded by -OR groups. Examples of R ¹ , R ² , R ³ and R ⁴ include -CH ₃ (methyl group), -C ₂ H ₅ (ethyl group), -CH (CH ₃ ) ₂ (isopropyl group) or A chain alkyl group composed only of C and H, such as —C (CH ₃ ) ₃ (tertiarybutyl group), A structure having O or N in a part of the chain such as —C ₂ H ₄ OCH ₃ (methoxyethyl group) may be used. Further, depending on the types of R ¹ , R ² , R ³ and R ⁴ , O or N can be coordinated to the metal element A, and the vaporization temperature when vaporizing the raw material is reduced as will be described later. Or stability in the raw material state can be increased.

  Next, the second source gas used in the ferroelectric film forming method according to the first embodiment of the present invention will be described. The second source gas is composed of a second organometallic compound containing a metal element B represented by the following general formula (2).

B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) (2)

Here, B is a pentavalent metal or a metal compound containing a pentavalent metal in an arbitrary ratio, R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different, and C and H And an organic group in which O or N may be added or O or N may not be added.

  The molecular structure of the second organometallic compound will be described with reference to FIG. In FIG. 3, a solid line indicates an ionic bond or a covalent bond.

As shown in FIG. 3, the metal element B is composed of 6 pieces. Surrounded by -OR groups. Examples of R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ include -CH ₃ (methyl group), -C ₂ H ₅ (ethyl group), -CH (CH ₃ ) ₂ (isopropyl group) or -C (CH ₃ ) ₃ (tertiary butyl group) and the like include chain alkyl groups composed only of C and H. The raw materials using these chain alkyl groups are liquid or solid at room temperature. is there. Therefore, in the case of a solid, it may be dissolved in an organic solvent to form a solution, and even if it is originally a liquid, it may be a solution dissolved in an organic solvent in order to obtain a necessary viscosity or the like.

  The first organometallic compound and the second organometallic compound are stored in a predetermined raw material container and used in a necessary amount. Since a chemical reaction usually occurs when the first organometallic compound and the second organometallic compound are mixed, the first organometallic compound and the second organometallic compound are accommodated in separate raw material containers. . However, in the case where the chemical reaction between the first organometallic compound and the second organometallic compound is suppressed by adding an additive such as amine, the first organometallic compound and the second organometallic are used. You may use the gas which mixed the compound beforehand.

  Further, the first organometallic compound and the second organometallic compound are vaporized using a bubbling method, a flash method, a mist vaporizing method, or the like to obtain a first source gas and a second source gas. In addition, the first source gas and the second source gas are heated and maintained in a gaseous state so that a necessary vapor pressure is obtained. In addition, the first source gas and the second source gas are mixed in a vaporizer, and further, an inert gas such as argon and an oxidizing gas such as oxygen gas, ozone gas or nitrogen monoxide gas are mixed. The raw material mixed gas is transported into the chamber.

  In the chamber, the raw material mixed gas is supplied to the vicinity of the surface of the substrate 1 through the shower head. The substrate 1 is heated to maintain a predetermined substrate temperature, and the raw material mixed gas undergoes a chemical reaction and thermal decomposition at the predetermined substrate temperature, whereby the ferroelectric film 11a is formed on the first electrode 10. Is deposited. In the method for forming a ferroelectric film according to the first embodiment of the present invention, the ferroelectric film 11a is formed on the first electrode 10 by intermolecular chemical reaction and thermal decomposition in the raw material mixed gas. The substrate temperature is kept near the temperature at which the raw material mixed gas undergoes thermal decomposition. Since the first organometallic compound and the second organometallic compound usually undergo thermal decomposition around 300 ° C., the substrate temperature is set to about 300 ° C.

  Here, since the ferroelectric film 11a deposited on the first electrode 10 contains a metal oxide as a main component and a part of the organic component remains, the ferroelectric film 11a is interatomic. It is a gel state in which a network is formed but not crystallized.

  Next, using a furnace or an RTA (Rapid Thermal Anneal) apparatus, the ferroelectric film 11a deposited on the first electrode 10 is subjected to a heat treatment at a temperature higher than that necessary for crystallization. As a result, the organic component in the ferroelectric film 11a is removed and the ferroelectric film 11a is crystallized, so that the ferroelectric film 11 having a bismuth layer structure, which is the final target, is formed on the first electrode 10. Can get to.

  Here, a chemical reaction caused by the first source gas and the second source gas in the source mixed gas will be described with reference to FIGS.

  The first source gas made of the first organometallic compound shown in FIG. 2 and the second source gas made of the second organometallic compound shown in FIG. 3 are under the substrate temperature near the thermal decomposition temperature, A chemical reaction represented by the following general reaction formula (a) occurs in the vicinity of the substrate surface.

A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ + 2B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ )
→ A [B Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ )] ₂
... (a)

That is, the first organometallic compound and the second organometallic compound undergo a chemical reaction, and a third organometallic compound containing bismuth and metal elements A and B is formed as shown in FIG. In FIG. 4, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are not shown for simplification, but R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are actually bonded to each oxygen atom.

  Here, the crystal structure of the ferroelectric film 11 having a finally formed bismuth layer structure will be described with reference to FIG.

  FIG. 5 shows the crystal structure of the ferroelectric film 11 having a bismuth layer structure. As is clear from FIG. 5, the crystal structure of the ferroelectric film 11 having a bismuth layer structure includes the metal shown in FIG. The same structure as a molecular structure having an atomic arrangement consisting of atoms and oxygen atoms is included. That is, immediately after the ferroelectric film 11a is formed on the first electrode 10 by the MOCVD method, the ferroelectric film 11a has atoms in the crystal structure of the ferroelectric film 11 having a bismuth layer structure. Since a part of the arrangement is already included, the activation energy required for crystallization of the ferroelectric film 11a formed on the first electrode 10 is reduced, so that the ferroelectric film Even if the temperature of the heat treatment required to crystallize 11a is lowered, the ferroelectric film 11a can be sufficiently crystallized.

  By the way, in the conventional method for forming a ferroelectric film using a source gas made of an organometallic compound containing metal elements A and B and a source gas made of an organometallic compound containing bismuth, the above-described effects cannot be obtained. . The reason will be described below.

  An organometallic compound containing metal elements A and B used in a conventional method for forming a ferroelectric film is represented by the following general formula (b).

^{A [B (OR 14) (} OR 15) (OR 16) (OR 17) (OR 18) (OR 19)] 2 ··· (b)

Here, A is a metal compound containing a divalent metal or a divalent metal in an arbitrary ratio, and B is a metal compound containing a pentavalent metal or a pentavalent metal in an arbitrary ratio. R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ may be the same or different and may contain C and H and may have O or N added thereto. Is an organic group that may not be added.

  The molecular structure of the organometallic compound represented by the general formula (b) will be described with reference to FIG. In FIG. 6, a solid line indicates an ionic bond or a covalent bond, and a broken line indicates a coordination bond. In practice, it is difficult to distinguish between coordination bonds and other bonds.

As shown in FIG. 6, the metal element A has a structure sandwiched between metal elements B through oxygen, and B is composed of six pieces. Surrounded by -OR groups. On the other hand, although the molecular structure of the first of the first organometallic compound constituting the first raw material gas used in the method for forming a ferroelectric film according to an embodiment of the present invention is as shown in FIG. 2, FIG. comparing the molecular structure shown in the molecular structure and Figure 6 shown in 2, while Bi-O-a bond is formed at the molecular structure shown in FIG. 2, the molecular structure shown in FIG. 6 Is formed with an A—O—B bond.

Bi-O Since the bond energy is inherently high, the Bi—O— A bond is energetically higher and unstable than the A—O—B bond. Therefore, since the Bi—O— A bond in FIG. 2 is energetically unstable, the Bi—O— A bond reacts with the metal element B to form a more stable A—O—B bond. On the other hand, since the A—O—B bond in FIG. 6 is energetically stable, it is difficult to cause a reaction with a molecule containing bismuth. Therefore, the conventional method of forming a ferroelectric film using an organometallic compound containing the metal elements A and B cannot obtain the operation of the present invention.

  Hereinafter, although one Example about the formation method of the ferroelectric film which has a bismuth layered structure concerning a 1st embodiment of the present invention is described, the present invention is not limited to the following examples.

First, the first organometallic compound is prepared by the following procedure. That is, strontium (Sr) is dissolved in ethanol (C ₂ H ₄ OH) and reacted at 78 ° C. to obtain a strontium solution. Then, bismuth triethoxide _{(Bi (OC 2 H 5)} 2) molar ratio of strontium solution solution 2: to be 1, bismuth triethoxide _{(Bi (OC 2 H 5)} 2) The solution is added to the strontium solution and refluxed, for example at a temperature of 78 ° C. for 2 hours. Thereby, a double alkoxide Sr [Bi (OC ₂ H ₅ ) ₄ ] ₂ solution of strontium bismuth is obtained as the first organometallic compound.

On the other hand, a commercially available tantalum pentaethoxide (Ta (OC ₂ H ₅ ) ₅ ) solution is used as the second organometallic compound.

  The first organometallic compound and the second organometallic compound are placed in each raw material bottle, and the flow rate from each raw material bottle is controlled by a liquid mass flow controller, while the first organometallic compound and the second organometallic compound are used. Is supplied to the vaporizer. An injector corresponding to each of the first and second organometallic compounds is provided in the vaporizer, and the first and second organometallic compounds are jetted into the vaporizer held at a low pressure at a stretch. By atomizing and gasifying in a vaporizer maintained at 200 ° C., for example, a first source gas and a second source gas are obtained.

  Furthermore, the first source gas and the second source gas are mixed with the carrier gas, argon gas, and the oxidizing gas, oxygen gas, and transported to the chamber as a source gas mixture. The raw material mixed gas transported to the chamber is supplied to the vicinity of the surface of the substrate 1 through a shower head. Since the substrate temperature is set to 300 ° C. near the temperature at which thermal decomposition occurs, the raw material mixed gas undergoes a chemical reaction represented by the following general reaction formula (c) and also undergoes thermal decomposition. A ferroelectric film 11 a is formed on the substrate 10.

Sr [Bi (OC ₂ H ₅ ) ₄ ] ₂ + 2Ta (OC ₂ H ₅ ) ₅
→ Sr [BiTa (OC ₂ H ₅ ) ₉ ] ₂

  The ferroelectric film 11a thus formed on the first electrode 10 is heat-treated in an oxygen atmosphere at, for example, 750 ° C. for 1 minute using an RTA apparatus, thereby providing a bismuth layer structure. Can be formed.

As described above, according to the first embodiment, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ And a first organometallic compound represented by the formula: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) The ferroelectric film 11a formed by causing a chemical reaction and thermal decomposition with the second organometallic compound represented by From a third organometallic compound represented by Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ )] ₂ Become. Therefore, the ferroelectric film 11a formed on the first electrode 10 by the MOCVD method is a part of the atomic arrangement in the crystal structure of the ferroelectric film 11 having a bismuth layer structure that is finally formed. Since the activation energy required for crystallization of the ferroelectric film 11a formed on the first electrode 10 to form the ferroelectric film 11 is reduced, Even if the temperature of the heat treatment for crystallizing the ferroelectric film 11a is lowered, the ferroelectric film 11a can be sufficiently crystallized. Therefore, as shown in FIG. 1, even when the oxygen barrier film 9 is formed between the first electrode 10 and the contact plug 6, at a temperature that satisfies the heat resistance limit of the oxygen barrier film 9. Crystallization of the ferroelectric film 11a becomes possible. In addition, a ferroelectric film having excellent step coverage and a desired composition can be formed.

(Second Embodiment)
Hereinafter, a method of forming a ferroelectric film having a bismuth layer structure according to the second embodiment of the present invention will be described with reference to FIGS.

  According to the method for forming a ferroelectric film according to the first embodiment described above, the heat treatment required for crystallizing the ferroelectric film 11a formed on the first electrode 10 is performed at a low temperature. Although it is an excellent method in that it can be performed, since the temperature at which the first organometallic compound is vaporized is high, there is a problem that the process margin is small.

  The method for forming a ferroelectric film according to the second embodiment of the present invention further solves this problem. By using the first organometallic compound having a high vaporization temperature, a process margin can be obtained. While enlarging, the effect similar to 1st Embodiment mentioned above is implement | achieved.

  Also in the second embodiment, as in the first embodiment, the first source gas made of the first organometallic compound, the second source gas made of the second organometallic compound, and the oxidizing gas are chambered. A ferroelectric film 11a (not shown) is formed on the first electrode 10 by MOCVD, and the ferroelectric film 11a is heat-treated and crystallized. Thus, the ferroelectric film 11 having a bismuth layer structure is formed. The MOCVD method is a method of forming a film on the first electrode 10 by causing a chemical reaction between the first source gas, the second source gas, and the oxidizing gas at a predetermined substrate temperature. .

  First, the first source gas used in the ferroelectric film forming method according to the second embodiment of the present invention will be described. The first source gas is composed of a first organometallic compound containing bismuth and a metal element A represented by the following general formula (3).

A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ ... (3)

Here, A is a divalent metal or a metal containing a divalent metal in an arbitrary ratio, and R ¹ , R ² , R ³ and R ⁴ are the same or different and contain C and H An organic group in which O or N may be added or O or N may not be added. R ²¹ , R ²² and R ²³ are the same or different and contain a hydrogen group or at least C and H and may have O or N added thereto, or may not have O or N added thereto. There are also organic groups.

  The molecular structure of the first organometallic compound will be described with reference to FIG. In FIG. 7, a solid line indicates an ionic bond or a covalent bond, and a broken line indicates a coordinate bond. In practice, it is difficult to distinguish between coordination bonds and other bonds.

As shown in FIG. 7, the metal element A has a structure sandwiched between oxygen and bismuth. Surrounded by -OR groups. Further, the metal element A is further coordinated with two amines NR ²¹ NR ²² NR ²³ . Examples of R ¹ , R ² , R ³ and R ⁴ include -CH ₃ (methyl group), -C ₂ H ₅ (ethyl group), -CH (CH ₃ ) ₂ (isopropyl group) or Examples thereof include a chain alkyl group composed only of C and H such as —C (CH ₃ ) ₃ (tertiarybutyl group). Further, as NR ²¹ , NR ²² or NR ²³ , for example, -H (hydrogen group), -CH ₃ (methyl group), -C ₂ H ₅ (ethyl group), —CH ₂ OH (methanol group) or -C ₂ H ₄ OH (ethanol group).

  Next, the second source gas used in the method for forming a ferroelectric film according to the second embodiment of the present invention will be described. The second source gas is made of the second organometallic compound containing the metal element B represented by the following general formula (4) as in the first embodiment.

B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) (4)

Here, B is a pentavalent metal or a metal containing a pentavalent metal in any ratio, and R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different, and C and H And an organic group in which O or N may be added or O or N may not be added.

  The molecular structure of the second organometallic compound is also the same as that in FIG. 3 shown in the first embodiment.

  Next, a first source gas composed of the first organometallic compound represented by the general formula (3) and a second source gas composed of the second organometallic compound represented by the general formula (4) are used. Then, after the ferroelectric film 11a is formed on the first electrode 10 by the MOCVD method, the ferroelectric film 11 is formed by subjecting the ferroelectric film 11a to heat treatment and crystallization. This is performed in the same manner as in the first embodiment.

  Here, a chemical reaction caused by the first source gas and the second source gas will be described with reference to FIGS.

  The first organometallic compound shown in FIG. 7 and the second organometallic compound shown in FIG. 2 are expressed by the following general reaction formula (c) near the substrate surface under the substrate temperature near the thermal decomposition temperature. Cause a chemical reaction.

A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂
+ 2B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ )
→ A [B Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ )] ₂ + 2NR ²¹ NR ²² NR ^23. )

  In this way, the first organometallic compound and the second organometallic compound cause a chemical reaction to form a third organometallic compound containing bismuth and metal elements A and B having the structure shown in FIG. Therefore, it has the same effect as the first embodiment. That is, the ferroelectric film 11a formed on the first electrode 10 by the MOCVD method already has a part of the atomic arrangement in the crystal structure of the ferroelectric film 11 having the bismuth layer structure. Since the activation energy required for crystallization of the ferroelectric film 11a to form the ferroelectric film 11 is reduced, the ferroelectric film 11a can be crystallized at a low temperature. Therefore, as shown in FIG. 1, even when the oxygen barrier film 9 is formed between the first electrode 10 and the contact plug 6, the temperature satisfies the heat resistance limit of the oxygen barrier film 9. The ferroelectric film 11a can be crystallized. In addition, a ferroelectric film having an excellent step coverage and a desired composition can be formed.

  Furthermore, in the second embodiment, unlike the first embodiment, two amines are coordinated and bonded to the metal element A of the first organometallic compound, thereby further providing the following effects. Have.

That is, the first organic metal compound used in the first embodiment, as shown in FIG. 2, since no electrically shielding due to the presence of spatially gap around the metal element A, Intermolecular force occurs in the space where the gap exists. In general, it is known that the vaporization temperature rises when intermolecular force acts, and the vaporization temperature of the first organometallic compound is high. Therefore, in order to lower the vaporization temperature of the first organometallic compound, it is only necessary to reduce the intermolecular force. Therefore, the metal element A may be electrically shielded. Therefore, in the first organometallic compound used in the second embodiment of the present invention, as shown in FIG. 7, two amines are coordinated to the metal element A to electrically connect the metal element A. Shielded. Thereby, the 1st organometallic compound shown in FIG. 7 can obtain the low vaporization temperature for using it for an actual process.

  Hereinafter, an example of a method for forming a ferroelectric film having a bismuth layer structure according to the second embodiment of the present invention will be described, but the present invention is not limited to the following example.

First, the first organometallic compound is prepared by the following procedure. Strontium (Sr) is dissolved in ethanol (C ₂ H ₄ OH) and reacted at, for example, 78 ° C. to obtain a strontium solution. Next, the bismuth triethoxide (Bi (OC ₂ H ₅ ) ₂ ) solution is added to the strontium solution so that the molar ratio of the bismuth triethoxide (Bi (OC ₂ H ₅ ) ₂ ) solution to the strontium solution is 2: 1. In addition, the mixture is refluxed at 78 ° C. for 2 hours, for example. Next, the diethanolamine (NH (C ₂ H ₄ OH) ₂ ) solution is added to the strontium solution so that the molar ratio of the diethanolamine (NH (C ₂ H ₄ OH) ₂ ) solution to the strontium solution is 2: 1. For example, the mixture is refluxed at 60 ° C. for 1 hour. Thus, strontium bismuth double alkoxide Sr [Bi ₂ (OC ₂ H ₅ ) ₄ ] ₂ (NH (C ₂ H ₄ OH) ₂ ) _{2 in} which an amine is coordinated as the first organometallic compound is obtained.

On the other hand, as the second organometallic compound, a commercially available tantalum pentaethoxide (Ta (OC ₂ H ₅ ) ₅ ) solution is used as in the first embodiment.

  The first organometallic compound and the second organometallic compound are placed in each raw material bottle, and the flow rate from each raw material bottle is controlled by a liquid mass flow controller, while the first organometallic compound and the second organometallic compound are used. Is supplied to the vaporizer. An injector corresponding to each of the first and second organometallic compounds is provided in the vaporizer, and the first and second organometallic compounds are jetted into the vaporizer held at a low pressure at a stretch. By atomizing and gasifying in a vaporizer maintained at 200 ° C., a first source gas and a second source gas are obtained.

  Furthermore, the first source gas and the second source gas are mixed with the carrier gas, argon gas, and the oxidizing gas, oxygen gas, and transported to the chamber as a source gas mixture. The raw material mixed gas transported to the chamber is supplied to the vicinity of the surface of the substrate 1 through a shower head. Since the substrate temperature is set to 300 ° C., which is near the temperature at which thermal decomposition occurs, the raw material mixed gas undergoes a chemical reaction represented by the following general reaction formula and undergoes thermal decomposition. Then, a ferroelectric film 11a is deposited.

Sr [Bi (OC ₂ H ₅ ) ₄ ] ₂ (NH (C ₂ H ₄ OH) ₂ ) ₂ + 2Ta (OC ₂ H ₅ ) ₅
→ Sr [BiTa (OC ₂ H ₅ ) ₉ ] ₂ + 2NH (C ₂ H ₄ OH) ₂

  The ferroelectric film 11a thus deposited on the first electrode 10 is heat-treated in an oxygen atmosphere, for example, at 750 ° C. for 1 minute using an RTA apparatus, thereby forming a bismuth layer structure. The ferroelectric film 11 having the same can be formed.

As described above, according to the second embodiment, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ And a first organometallic compound represented by the formula: B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) The ferroelectric film 11a formed by causing a chemical reaction and thermal decomposition with the second organometallic compound represented by From a third organometallic compound represented by Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ )] ₂ Become. Therefore, in the ferroelectric film 11a formed on the first electrode 10 by the MOCVD method, a part of the atomic arrangement of the ferroelectric film 11 having a bismuth layer structure that is finally formed is already present. Therefore, the activation energy required for crystallization of the ferroelectric film 11a deposited on the first electrode 10 to form the ferroelectric film 11 is reduced. Even if the temperature of the heat treatment for crystallizing the film 11a is lowered, the ferroelectric film 11a can be sufficiently crystallized. Therefore, as shown in FIG. 1, even when the oxygen barrier film 7 is formed between the first electrode 10 and the contact plug 6, the temperature satisfies the heat resistance limit of the oxygen barrier film 7. The ferroelectric film 11a can be crystallized. In addition, a ferroelectric film having an excellent step coverage and a desired composition can be formed.

Furthermore, according to the second embodiment, A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ In the first organometallic compound represented by the formula, since two amines are coordinated to the metal element A, the metal element A is electrically shielded and the intermolecular force is reduced. The organometallic compound can obtain a low vaporization temperature for use in an actual process, and can increase a process margin.

(Third embodiment)
A method for forming a ferroelectric film according to the third embodiment of the present invention will be described below.

  The method for forming a ferroelectric film according to the third embodiment is a method for further lowering the heating temperature for crystallization of the ferroelectric film 11a than in the above-described embodiments. Therefore, the raw material used in the present embodiment and the method for vaporizing the raw material are the same as those described in the previous embodiments. In addition, the ferroelectric film forming method according to the third embodiment is performed after the first source gas made of the first organometallic compound and the second source gas made of the second organometallic compound are formed. Since it has characteristics, the characteristic part will be described below.

  The first source gas and the second source gas are mixed in a vaporizer, and further into an inert gas such as argon, an oxidizing gas such as oxygen gas, ozone gas or nitrogen monoxide gas, and water vapor. It is mixed and transported into the chamber as a raw material mixed gas.

  In the chamber, the raw material mixed gas is supplied to the vicinity of the surface of the substrate 1 through the shower head. The substrate 1 is heated to maintain a predetermined substrate temperature, and under this predetermined substrate temperature, the raw material mixed gas undergoes a chemical reaction represented by the general reaction formula (a) or (c) and also causes thermal decomposition. Thus, the ferroelectric film 11 a is formed on the first electrode 10. The substrate temperature is set to about 300 ° C. as in the above embodiments.

  In this way, the ferroelectric film 11a formed on the first electrode 10 undergoes the chemical reaction shown in the general reaction formula (a) or (c), and then the molecules after the reaction further shrink. Causes a polymerization reaction. For this reason, since a polymer network of metal and oxygen is formed in the ferroelectric film 11a, the heating temperature for crystallizing the ferroelectric film 11a is set to a lower temperature, and the ferroelectric film The ferroelectric film 11 having a bismuth layer structure can be formed by crystallizing the film 11a.

In each of the above embodiments, the general formula of the bismuth layer structure is obtained by using the first source gas made of the first organometallic compound and the second source gas made of the second organometallic compound. ^{_{Bi 2 O 2) 2+ (a}} m-1 B m O 3m + 1) in ^2-, m = when it is ^{_{2 (Bi 2 O 2) 2+}} (AB 2 O 7) represented by ^2- Although the case where a ferroelectric film having a bismuth layer structure is formed has been described, the present invention is not limited to this. For example, by further using an organometallic compound represented by Ti (OR ¹¹ ) (OR ¹² ) (OR ¹³ ) (OR ¹⁴ ), (Bi ₂ O ₂ ) ²⁺ (A in _{m-1 B m O 3m +} 1) 2-, a ferroelectric having a ^{_{(Bi 2 O 2) 2+ (}} a 2 B 3 O 10) bismuth layer structure represented by ² when it is m = 3 A body membrane can also be formed.

  Moreover, although the case where only two types of the first organometallic compound containing bismuth and the metal element A and the second organometallic compound containing the metal element B are used as raw materials has been described, the organometallic compound or metal containing bismuth An organometallic compound containing element A may be further added as a raw material, or an organometallic compound containing metal elements A and B or an organometallic compound containing bismuth and metal element B may be used as a raw material. As described above, since the composition ratio of the ferroelectric film can be easily controlled by using or combining each raw material in an auxiliary manner, a ferroelectric film having an optimum composition ratio can be formed.

  As described above, according to the first method for forming a ferroelectric film of the present invention, a ferroelectric film having a bismuth layer structure can be formed by crystallization by heat treatment at a low temperature. A ferroelectric capacitor element having the following can be manufactured.

It is sectional drawing which shows an example of the capacitive element which has the ferroelectric film formed with the formation method of the ferroelectric film which concerns on each embodiment. It is a molecular structure figure of the 1st organometallic compound concerning a 1st embodiment. It is a molecular structure figure of the 2nd organometallic compound concerning a 1st embodiment. It is a molecular structure figure of the 3rd organometallic compound containing bismuth and metal elements A and B concerning a 1st embodiment. It is a crystal structure diagram of a ferroelectric film having a bismuth layer structure. It is a molecular structure diagram of an organometallic compound containing metal elements A and B used in a conventional method for forming a ferroelectric film. It is a molecular structure figure of the 1st organometallic compound concerning a 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Impurity diffusion layer 3 Gate electrode 4 Field effect transistor 5 Protective insulating film 6 Contact plug 7 Opening portion 8 Interlayer insulating film 9 Oxygen barrier film 10 First electrode 11 Ferroelectric film 12 Second electrode

Claims (4)

In the chamber, at least,
A first source gas composed of a first organometallic compound represented by the following general formula (1);
A second source gas composed of a second organometallic compound represented by the following general formula (2);
A method of forming a ferroelectric film having a bismuth layer structure, comprising a step of introducing an oxidizing gas and forming a film by metal organic chemical vapor deposition.
A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (1)
(However, A is a metal compound containing a divalent metal or a divalent metal in an arbitrary ratio,
R ¹ , R ² , R ³ and R ⁴ are the same or different, and are organic groups containing C and H. )
B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) (2)
(However, B is a metal compound containing pentavalent metal or pentavalent metal in an arbitrary ratio,
R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different, and are organic groups containing C and H. ) In the chamber, at least,
A first source gas composed of a first organometallic compound represented by the following general formula (3);
A second source gas composed of a second organometallic compound represented by the following general formula (4);
A method of forming a ferroelectric film having a bismuth layer structure, comprising a step of introducing an oxidizing gas and forming a film by metal organic chemical vapor deposition.
A [Bi (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )] ₂ (NR ²¹ NR ²² NR ²³ ) ₂ (3)
(However, A is a metal compound containing a divalent metal or a divalent metal in an arbitrary ratio,
R ¹ , R ² , R ³ and R ⁴ are the same or different and are organic groups containing C and H;
R ²¹ , R ²² and R ²³ are the same or different, and are a hydrogen group or an organic group containing C and H. )
B (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (OR ⁸ ) (OR ⁹ ) (4)
(However, B is a metal compound containing pentavalent metal or pentavalent metal in an arbitrary ratio,
R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different, and are organic groups containing C and H. ) 3. The method of forming a ferroelectric film according to claim 1, wherein the ferroelectric film is represented by (Bi ₂ O ₂ ) ²⁺ (AB ₂ O ₇ ) ²⁻ . The method for forming a ferroelectric film according to claim 1, further comprising a step of introducing water vapor into the chamber.

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