JP2005191358A - Method for heat treatment of ferroelectric film, capacity element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for heat treatment of a ferroelectric film by which the generation of oxygen omission in the ferroelectric film is suppressed. <P>SOLUTION: The method for the heat treatment of the ferroelectric film comprises processes for performing: first heat treatment for preventing oxygen in the ferroelectric film from being diffused to the outside of the ferroelectric film, and second heat treatment for crystallizing the ferroelectric film after the process for performing the first heat treatment. In the process for performing the first heat treatment, it is preferable to perform the heat treatment under an atmosphere that ozone concentration is ≥0.7% and ≤2.0% and a condition that temperature is ≥450°C and ≤550°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a capacitive element and a manufacturing method thereof, and more particularly to a heat treatment method for a ferroelectric film used for a capacitive insulating film constituting the capacitive element.

  In recent years, in the development of a nonvolatile memory using a ferroelectric film, it is required to improve the polarization characteristics of the ferroelectric film in order to cope with the trend toward miniaturization of devices. In particular, the polarization characteristics of the ferroelectric film vary greatly depending on the heat treatment method for crystallizing the ferroelectric film.

  By the way, in the ferroelectric film, a film in which oxygen is deficient in the film, that is, a film in which oxygen deficiency (oxygen depletion) occurs in the film is easily formed. Oxygen deficiency (oxygen vacancies) leads to a decrease in dielectric constant, an increase in leakage current, a decrease in remanent polarization, or an increase in coercive electric field. Therefore, oxygen deficiency (oxygen depletion) has a desired dielectric property or ferroelectric property. This is a great adverse effect in obtaining a film having the same.

  Such oxygen vacancies occur in the process of forming a ferroelectric film using the MOD method or the CVD method. The following reasons are considered as the reason why oxygen vacancies (oxygen vacancies) occur.

  That is, in the case of using the MOD method, after a thin film is deposited from a raw material compound having no metal-oxide bond, heat treatment is performed in an oxygen atmosphere. A metal-oxygen bond is formed based on the solid phase diffusion of oxygen by this heat treatment, and a ferroelectric film that is an oxide is formed. Accordingly, oxygen vacancies (oxygen vacancies) are likely to occur in the ferroelectric film.

  On the other hand, when using the CVD method, the oxidation state of the deposited thin film differs greatly depending on whether or not the raw material compound has a metal-oxygen bond in the molecule, but currently available bismuth (Bi) raw material is triphenylbismuth and its Only similar compounds, these compounds do not have metal-oxygen bonds. For this reason, when depositing a bismuth layered ferroelectric film using the CVD method, a two-stage reaction of a stage of decomposition of triphenylbismuth and generation of metal bismuth and a stage of oxidation of metal bismuth by oxygen in the atmosphere. is required. Therefore, it is difficult to avoid the formation of a ferroelectric film containing oxygen vacancies (oxygen vacancies).

  Thus, the problem of oxygen deficiency (oxygen depletion) cannot be solved by either the MOD method or the CVD method. Thus, development of a new raw material compound or development of a new method for forming a ferroelectric film is awaited.

Under such circumstances, after forming the ferroelectric film, the ferroelectric film is subjected to post-annealing (heat treatment) in which heat treatment is performed in oxygen gas, whereby oxygen vacancies (oxygen vacancies) are formed. It is thought that the best way to solve this problem is to solve the problem of oxygen deficiency (oxygen vacancies) by heat-treating the ferroelectric film in an active oxygen atmosphere. It has been proposed (see, for example, Patent Document 1).
JP-A-9-69615 (page 3, paragraph 0007)

  However, even in these methods, in most cases, the problem of oxygen deficiency (oxygen vacancies) in the ferroelectric film cannot be sufficiently solved. For this reason, bismuth is present as a metal without being oxidized on the surface layer of the ferroelectric film, or defects are generated in the ferroelectric film due to heat treatment performed in an oxygen gas at a high temperature of usually about 800 ° C. Will occur.

  In view of the above, an object of the present invention is to improve the polarization characteristics of a ferroelectric film by preventing oxygen deficiency from occurring in the ferroelectric film.

  In order to achieve the above object, a ferroelectric film heat treatment method according to the present invention is a ferroelectric film heat treatment method including a step of performing a heat treatment on a ferroelectric film, wherein the heat treatment is performed. In the step, the first heat treatment for preventing oxygen in the ferroelectric film from diffusing outside the ferroelectric film and the step of performing the first heat treatment are performed after the ferroelectric film is crystallized. And a second heat treatment step.

  According to the heat treatment method for a ferroelectric film according to the present invention, oxygen in the ferroelectric film diffuses outside before the second heat treatment for crystallizing the ferroelectric film as the heat treatment for the ferroelectric film. Since the first heat treatment for preventing this is performed, oxygen vacancies in the ferroelectric film can be suppressed. Thereby, a ferroelectric film having excellent polarization characteristics can be obtained.

  In the ferroelectric film heat treatment method according to the present invention, the first heat treatment is performed at a temperature of 450 ° C. or higher in an atmosphere having an ozone concentration of 0.7% or more and 2.0% or less. And it is preferably carried out under conditions of 550 ° C. or lower.

  In this case, the first heat treatment for the ferroelectric film is performed using ozone gas at a temperature in the range of 450 ° C. or more and 550 ° C. or less before the second heat treatment for crystallizing the ferroelectric film. Therefore, oxygen deficiency in the ferroelectric film due to solid phase diffusion can be suppressed. Moreover, since ozone gas is used for the first heat treatment, oxygen diffusion from the ferroelectric film to the outside can be further suppressed. Thereby, a ferroelectric film having excellent polarization characteristics can be obtained.

  In order to achieve the above object, a capacitive element according to the present invention includes a capacitive lower electrode formed on a substrate, a capacitive insulating film made of a ferroelectric film formed on the capacitive lower electrode, A capacitive element including a capacitive upper electrode formed on a capacitive insulating film, wherein a conductive oxide film is formed between the capacitive lower electrode and the capacitive insulating film.

  According to the capacitive element of the present invention, since the conductive oxide film is formed between the capacitor lower electrode and the ferroelectric film, the solid-phase diffusion is performed during the heat treatment for crystallizing the ferroelectric film. Oxygen vacancies in the ferroelectric film can be suppressed. Thereby, a ferroelectric capacitor having excellent polarization characteristics can be obtained.

In the capacitor according to the present invention, the capacitor lower electrode is preferably made of an Ir film or an IrO _x film.

  In this way, a conductive oxide film can be easily formed at the interface between the ferroelectric film and the capacitor lower electrode.

  In order to achieve the above object, a method of manufacturing a capacitive element according to the present invention includes a step of forming a capacitive lower electrode on a substrate, and a capacitive insulating film made of a ferroelectric film on the capacitive lower electrode. A method of manufacturing a capacitive element comprising: a step of forming; a step of performing a heat treatment on the capacitor insulating film; and a step of forming a capacitor upper electrode on the capacitor insulating film. A first heat treatment for preventing oxygen in the film from diffusing into the capacitor lower electrode or the capacitor upper electrode, and a second heat treatment for crystallizing the ferroelectric film after the first heat treatment. And performing the process.

  According to the method for manufacturing a capacitor element of the present invention, the first heat treatment for preventing oxygen in the ferroelectric film from diffusing into the capacitor lower electrode before the second heat treatment for crystallizing the ferroelectric film. Thus, oxygen vacancies in the ferroelectric film can be suppressed. Thereby, a ferroelectric capacitor having excellent polarization characteristics can be manufactured.

  In the method for manufacturing a capacitive element according to the present invention, the step of performing the first heat treatment includes a temperature of 450 ° C. or higher in an atmosphere having an ozone concentration of 0.7% or higher and 2.0% or lower. And it is preferable to carry out under the condition of 550 ° C. or lower.

  In this case, the first heat treatment is performed using ozone gas at a temperature in the range of 450 ° C. or more and 550 ° C. or less before the second heat treatment for crystallizing the ferroelectric film. Oxygen vacancies in the ferroelectric film due to diffusion can be suppressed. In addition, since ozone gas is used in the first heat treatment, oxygen is supplied to the capacitor lower electrode, so that oxygen diffusion from the ferroelectric film to the outside can be further suppressed. Thereby, a ferroelectric capacitor having excellent polarization characteristics can be manufactured.

In the capacitive element manufacturing method according to the present invention, the capacitive lower electrode is preferably made of an Ir film or an IrO _x film.

  In this way, a conductive oxide film can be easily formed at the interface between the ferroelectric film and the capacitor lower electrode.

  According to the heat treatment method for a ferroelectric film according to the present invention, oxygen in the ferroelectric film diffuses outside before the second heat treatment for crystallizing the ferroelectric film as the heat treatment for the ferroelectric film. Since the first heat treatment for preventing this is performed, oxygen vacancies in the ferroelectric film can be suppressed. Thereby, a ferroelectric film having excellent polarization characteristics can be obtained.

  According to the capacitive element of the present invention, since the conductive oxide film is formed between the capacitor lower electrode and the ferroelectric film, the solid-phase diffusion is performed during the heat treatment for crystallizing the ferroelectric film. Oxygen vacancies in the ferroelectric film can be suppressed. Thereby, a ferroelectric capacitor having excellent polarization characteristics can be obtained.

  According to the method for manufacturing a capacitor element of the present invention, the first heat treatment for preventing oxygen in the ferroelectric film from diffusing into the capacitor lower electrode before the second heat treatment for crystallizing the ferroelectric film. Therefore, oxygen vacancies in the ferroelectric film due to solid phase diffusion can be suppressed. Thereby, a ferroelectric capacitor having excellent polarization characteristics can be manufactured.

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

(First embodiment)
In the first embodiment of the present invention, a heat treatment method for a ferroelectric film will be described.

  The method for heat treatment of a ferroelectric film according to the first embodiment of the present invention is a first heat treatment for a ferroelectric film that prevents oxygen in the ferroelectric film from diffusing outside the ferroelectric film. It is characterized in that the first heat treatment is performed, and then the second heat treatment for crystallizing the ferroelectric film is performed.

  The ferroelectric film heat treatment method according to the first embodiment of the present invention will be specifically described below with reference to FIGS.

In the first embodiment, for example, the following heat treatment is performed on a ferroelectric film made of an SBT (SrBi ₂ Ta ₂ O ₉ ) film formed by using the MOD method, the MOCVD method, the sputtering method, or the like.

  First, the first heat treatment for preventing oxygen in the ferroelectric film from diffusing outside the ferroelectric film will be described.

  The first heat treatment is performed so as to satisfy the heat treatment conditions shown in [Table 1] below. That is, the first heat treatment is performed in an atmosphere having an ozone concentration of 0.7% or more and 2.0% or less under a condition where the temperature is 450 ° C. or more and 550 ° C. or less.

In the first embodiment, more specifically, the first heat treatment is performed so as to satisfy the heat treatment conditions shown in [Table 2] below as an example. That is, the ozone flow rate is 3500 cc / min, the nitrogen flow rate is 28 cc / min, the ozone concentration is 200 g / m ³ (provided the flow rate is 20 l / min), the annealing temperature is 500 ° C., the annealing time is 10 min, and the temperature rising rate is 4 ° C. First heat treatment is performed under the conditions of / min and a temperature drop rate of 8 ° C./min.

  Next, a second heat treatment for crystallizing the ferroelectric film is performed. Here, as an example, the second heat treatment is performed so as to satisfy the heat treatment conditions shown in [Table 3] below. That is, for example, the oxygen flow rate is 10,000 cc / min, the nitrogen flow rate is 0 cc / min, the annealing temperature is 750 ° C. to 850 ° C., the annealing time is 1 min to 30 min, the heating rate is 60 ° C./min, and the cooling rate is not set. Under the conditions, a second heat treatment is performed.

  In this manner, the first heat treatment and the second heat treatment are performed as the heat treatment method for the ferroelectric film according to the first embodiment.

  Here, the relationship between the conditions of the first heat treatment and the polarization characteristics of the ferroelectric film will be described with reference to FIG.

FIG. 1 shows the relationship between the ozone concentration (%) of the first heat treatment and the polarization amount (μC / cm ² ) of the ferroelectric capacitor having the ferroelectric film after the first and second heat treatments are performed. Is shown. However, it is a relationship diagram when the temperature condition of the first heat treatment is 500 ° C.

  As is apparent from FIG. 1, the first heat treatment is performed while changing the ozone concentration while the temperature is set to 500 ° C., and the ferroelectric film having the ferroelectric film after the second heat treatment is performed. As a result, the polarization amount of the capacitor was proportional to the ozone concentration.

Furthermore, if the first heat treatment is performed under an atmosphere where the ozone concentration is 0.7% or more and 2.0% or less and the temperature is 450 ° C. or more and 550 ° C. or less, As a result, it was possible to realize a value of 13.5 (μC / cm ² ) or more as the polarization amount of the ferroelectric capacitor after the heat treatment. If the polarization amount of the ferroelectric capacitor is 13.5 (μC / cm ² ) or more, the polarization amount is sufficient for the storage capacity of the semiconductor device.

  In addition, when the condition of the second heat treatment is a constant condition (for example, the condition shown in the above [Table 3]), the temperature condition of the first heat treatment is any one within the range shown in the above [Table 1]. It has been found that the polarization amount of the ferroelectric capacitor is improved even under temperature conditions.

  Next, the reason why the conditions shown in the above [Table 1] must be satisfied as the conditions for the first heat treatment will be described.

  The lower limit temperature as the temperature condition of the first heat treatment is determined by a temperature necessary for nucleation of the SBT film constituting the ferroelectric film. This is because sufficient nucleation is not performed when the nucleation temperature is low, and the polarization amount of the ferroelectric capacitor having the ferroelectric film after the second heat treatment is reduced.

FIG. 2 shows the temperature [° C.] of the first heat treatment for the ferroelectric film and the polarization amount (μC / cm ^{2) of the} ferroelectric capacitor having the ferroelectric film after the first and second heat treatments are performed. ).

  As is apparent from FIG. 2, when the temperature of the first heat treatment is lower than 450 ° C., the amount of polarization of the ferroelectric capacitor decreases. Therefore, the lower limit temperature of the first heat treatment is preferably 450 ° C. On the other hand, when the temperature of the first heat treatment is increased, the C-axis orientation of the ferroelectric film after the second heat treatment becomes stronger, so that the polarization amount of the ferroelectric capacitor decreases. Therefore, the upper limit temperature of the first heat treatment is preferably 550 ° C.

  Further, if the temperature of the first heat treatment is 450 ° C. or higher and within the range of 550 ° C. or lower, if the lower limit concentration of ozone concentration is at least 0.7%, the ferroelectric material It has been found that it is effective in improving the polarization characteristics of the capacitor. Therefore, the lower limit concentration of the ozone concentration is preferably 0.7%. On the other hand, the upper limit of the ozone concentration was controlled by the performance of the diffusion furnace used in the experiment and was 2.0%, but the upper limit of the ozone concentration that can normally be generated in the diffusion furnace used for semiconductor devices (apparatus specifications) Is 2 to 3%, and the upper limit of the ozone concentration of the first heat treatment is obtained within the range.

  Next, a mechanism for improving the polarization characteristics of the ferroelectric capacitor having the ferroelectric film according to the present embodiment will be described.

  The first heat treatment is performed in a temperature region in which oxygen in the ferroelectric film does not solid-phase diffuse into an electrode (not shown), and this heat treatment is performed in an ozone atmosphere. As a result, a conductive oxide film having a high oxygen concentration can be formed at the interface between the ferroelectric film and the electrode. Therefore, during the second heat treatment for crystallizing the ferroelectric film at a high temperature, a solid oxide film is formed. Oxygen diffusion from the ferroelectric film to the electrode due to layer diffusion can be suppressed. In addition, after the nucleation of the ferroelectric film is performed by the first heat treatment at a low temperature, the ferroelectric capacitor having excellent polarization characteristics is obtained by performing the second treatment for nucleation at a high temperature. Can be realized. In addition, since the second heat treatment is performed in a temperature range of 750 ° C. to 850 ° C., the temperature range of the second heat treatment is a temperature region in which oxygen in the ferroelectric film is solid-phase diffused to the electrode. In addition to performing the heat treatment of 2 in a short time, a conductive oxide film having a high oxygen concentration is present at the interface between the ferroelectric film and the electrode. Since oxygen diffusion is suppressed, oxygen in the ferroelectric film does not diffuse into the electrode.

  As described above, according to the first embodiment of the present invention, as the heat treatment for the ferroelectric film, ozone gas is used at a low temperature before the second heat treatment for crystallizing the ferroelectric film at a high temperature. Since the first heat treatment is performed, oxygen vacancies in the ferroelectric film are suppressed and a conductive oxide film having a high oxygen concentration is formed on the surface of the ferroelectric film. Oxygen diffusion to the outside can be suppressed. Thereby, it is possible to realize a ferroelectric capacitor having excellent polarization characteristics by eliminating oxygen deficiency in the ferroelectric film due to heat treatment.

(Second Embodiment)
In the second embodiment of the present invention, refer to FIG. 3 for the structure of a capacitive element having a capacitive insulating film made of a ferroelectric film that has been subjected to the heat treatment method of the ferroelectric film in the first embodiment described above. While explaining.

  A capacitive element according to the second embodiment of the present invention includes a capacitive lower electrode formed on a substrate, a capacitive insulating film made of a ferroelectric film formed on the capacitive lower electrode, and an upper surface of the capacitive lower electrode. And a conductive oxide film is formed between the capacitor lower electrode and the capacitor insulating film.

As shown in FIG. 3, a conductive oxide film 2 having a high oxygen concentration is formed on a capacitor lower electrode 1 made of an Ir film or an IrO _x film formed on a substrate (not shown). A capacitive insulating film 3 made of a ferroelectric film is formed on the conductive oxide film 2. A capacitor lower electrode 4 is formed on the capacitor insulating film 3.

  As described above, in the capacitive element shown in FIG. 3, the conductive oxide film 2 having a high oxygen concentration is formed between the capacitive lower electrode 1 and the capacitive insulating film 3. The conductive oxide film 2 is formed by depositing a capacitor insulating film 3 made of a ferroelectric film on the capacitor lower electrode 1 and then forming the capacitor insulating film 3 with respect to the first described in the first embodiment. It is formed between the capacitor lower electrode 1 and the capacitor insulating film 3 by performing heat treatment.

  Here, according to the structure of the capacitive element according to the present embodiment, a mechanism for improving the polarization characteristics of the ferroelectric capacitor will be described.

  When the first heat treatment shown in [Table 1] is performed on the capacitor insulating film 3 made of a ferroelectric film deposited on the capacitor lower electrode 1, the ozone concentration is 0.7% or more. In addition, since the temperature is 450 ° C. or more and 550 ° C. or less in an atmosphere of 2.0% or less, the oxygen deficiency of the ferroelectric film is suppressed, and the capacitive insulating film 3 made of the ferroelectric film and A conductive oxide film 2 having a high oxygen concentration can be formed at the interface with the capacitor lower electrode 1. Since the conductive oxide film 2 having a high oxygen concentration exists at the interface between the capacitive insulating film 3 made of a ferroelectric film and the capacitive lower electrode 1, the second heat treatment for crystallizing the ferroelectric film at a high temperature. Sometimes, oxygen diffusion from the ferroelectric film to the capacitor lower electrode 1 due to solid layer diffusion can be suppressed.

  As described above, according to the second embodiment, the first heat treatment for the ferroelectric film is performed using ozone gas at a low temperature before the second heat treatment for crystallizing the ferroelectric film at a high temperature. Since the heat treatment is performed, the oxygen deficiency of the ferroelectric film is suppressed, and the presence of the conductive oxide film having a high oxygen concentration formed between the ferroelectric film and the capacitor lower electrode allows ferroelectrics due to solid layer diffusion. Oxygen diffusion from the body film to the capacitor lower electrode can be suppressed. In this manner, a ferroelectric capacitor having excellent polarization characteristics can be realized by eliminating oxygen deficiency in the ferroelectric film due to heat treatment.

(Third embodiment)
In the third embodiment, a description will be given of a method for manufacturing a capacitive element to which the ferroelectric film heat treatment method according to the first embodiment described above is applied. That is, a specific method for manufacturing the capacitive element according to the third embodiment will be described.

  First, as shown in FIG. 4A, a switching transistor 3 and an impurity diffusion region 4 serving as a source region or a drain region are formed in an element formation region partitioned by a shallow trench isolation film (STI film) 2 on a semiconductor substrate 1. Form. Next, a protective insulating film 5 is formed on the semiconductor substrate 1 and the isolation insulating film 2 so as to cover the switching transistor 3. Next, an opening serving as a capacitor element formation opening is formed in the protective insulating film 5 for each storage node. The opening is formed so as to penetrate the protective insulating film 5 and to expose the impurity diffusion region 4 at the lower end. Next, the storage node contact 6 is formed by filling the opening formed in the protective insulating film 5 with a tungsten film or a polysilicon film.

Next, the ferroelectric film is oxidized when the ferroelectric film formed later is crystallized so that the lower surface is connected to the upper end of the storage node contact 6 on the protective insulating film 5. An oxygen barrier film 7 to be prevented is formed. Next, an interlayer insulating film 8 is formed on the protective insulating film 5 so as to cover the oxygen barrier film 7. Next, after forming a concave opening in the interlayer insulating film 8, the capacitor lower electrode 9 whose lower surface is electrically connected to the upper surface of the oxygen barrier film 7 on the interlayer insulating film 8 including the concave opening. And then patterning the first conductive film using a desired mask so as to electrically isolate at least the storage node contacts from each other, thereby forming the first conductive film. A lower capacitor electrode 9 is formed. The first conductive film constituting the capacitor lower electrode 9 is made of an Ir film or an IrO _x film and has a thickness in the range of 50 to 200 nm.

  Next, as shown in FIG. 4B, after a ferroelectric film is deposited so as to cover the capacitor lower electrode 9 by MOCVD, MOD, sputtering, or the like, at least each of them is formed using a desired mask. By patterning the ferroelectric film using a desired mask so as to electrically isolate the storage node contacts, a capacitive insulating film 10 made of a ferroelectric film having a thickness of 50 to 200 nm is formed. .

  Next, as shown in FIG. 4 (c), the temperature of the capacitive insulating film 10 is in the range of 450 ° C. or higher and 550 ° C. or lower so as to satisfy the conditions shown in [Table 1]. Then, the first heat treatment is performed for 10 minutes when the ozone concentration is 0.7% or more and 2.0% or less. Thereby, as shown in the partial enlarged view on the right side of FIG. 4C, a conductive oxide film 9a having a high oxygen concentration is formed at the interface between the capacitor lower electrode 9 and the capacitor insulating film 10. Thereafter, a second heat treatment is performed on the capacitor insulating film 10 at a temperature of 850 ° C. for 1 minute in an oxygen atmosphere to crystallize the ferroelectric film constituting the capacitor insulating film 1.

  As described above, when the first heat treatment shown in the above [Table 1] is performed on the capacitor insulating film 10 made of the ferroelectric film deposited on the capacitor lower electrode 9, oxygen vacancies in the ferroelectric film are obtained. In addition, the conductive oxide film 9a having a high oxygen concentration can be formed at the interface between the capacitive insulating film 10 made of a ferroelectric film and the capacitive lower electrode 9. Since the conductive oxide film 9a having a high oxygen concentration exists at the interface between the capacitive insulating film 10 made of a ferroelectric film and the capacitive lower electrode 9, the second heat treatment for crystallizing the ferroelectric film at a high temperature. Sometimes, oxygen diffusion from the ferroelectric film to the capacitor lower electrode 9 due to solid layer diffusion can be suppressed.

Next, as shown in FIG. 4D, a second conductive film made of a Pt film, an Ir film, or IrO _x and having a thickness of 5 to 200 nm is deposited so as to cover the capacitive insulating film 10. Thereafter, the capacitor upper electrode 11 made of the second conductive film is formed by patterning the second conductive film using a desired mask so that at least the storage node contacts are electrically isolated from each other.

  As described above, according to the third embodiment, as the heat treatment for the ferroelectric film, the first heat treatment using ozone gas at a low temperature is performed before the second heat treatment for crystallizing the ferroelectric film at a high temperature. Since the heat treatment is performed, the oxygen deficiency of the ferroelectric film is suppressed, and the presence of the conductive oxide film having a high oxygen concentration formed between the ferroelectric film and the capacitor lower electrode allows ferroelectrics due to solid layer diffusion. Oxygen diffusion from the body film to the capacitor lower electrode can be suppressed. Thus, it is possible to manufacture a ferroelectric capacitor having excellent polarization characteristics by eliminating oxygen vacancies in the ferroelectric film due to heat treatment.

  According to the present invention, a ferroelectric film having excellent polarization characteristics can be obtained by suppressing oxygen vacancies in the ferroelectric film due to solid phase diffusion, so that the heat treatment of the ferroelectric film used for the capacitive insulating film This method is useful for a method, a capacitive element having a capacitive insulating film made of a ferroelectric film, and a method for manufacturing the same.

FIG. 3 is a relationship diagram between a polarization amount and an ozone concentration of the ferroelectric capacitor according to the first embodiment of the present invention. FIG. 3 is a relationship diagram between the polarization amount of the ferroelectric capacitor and the heat treatment temperature according to the first embodiment of the present invention. It is sectional drawing which shows the structure of the capacitive element which concerns on the 2nd Embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the capacitive element which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 9 Capacitor lower electrode 2, 9a Conductive oxide film 3, 10 Capacitor insulating film 4 made of a ferroelectric film, 11 Capacitor upper electrode 1 Substrate 2 Shallow trench isolation film 3 Switching transistor 4 Impurity diffusion layer 5 Protective insulating film 6 Storage node contact 7 Oxygen barrier film 8 Interlayer insulating film 9 Capacitor lower electrode

Claims (7)

A method for heat-treating a ferroelectric film having a step of heat-treating the ferroelectric film,
The step of performing the heat treatment includes
Performing a first heat treatment for preventing oxygen in the ferroelectric film from diffusing outside the ferroelectric film;
And a step of performing a second heat treatment for crystallizing the ferroelectric film after the step of performing the first heat treatment.   The step of performing the first heat treatment is performed under a condition where the temperature is 450 ° C. or more and 550 ° C. or less in an atmosphere having an ozone concentration of 0.7% or more and 2.0% or less. The method for heat-treating a ferroelectric film according to claim 1. A capacitor lower electrode formed on the substrate;
A capacitive insulating film made of a ferroelectric film formed on the capacitive lower electrode;
A capacitive element comprising a capacitive upper electrode formed on the capacitive insulating film,
A capacitor element, wherein a conductive oxide film is formed between the capacitor lower electrode and the capacitor insulating film. The capacitive element according to claim 3, wherein the capacitive lower electrode is made of an Ir film or an IrO _x film. Forming a capacitor lower electrode on the substrate;
Forming a capacitor insulating film made of a ferroelectric film on the capacitor lower electrode;
Performing a heat treatment on the capacitive insulating film;
Forming a capacitor upper electrode on the capacitor insulating film, comprising:
The step of performing the heat treatment includes
Performing a first heat treatment for preventing oxygen in the ferroelectric film from diffusing into the capacitor lower electrode or the capacitor upper electrode;
And a step of performing a second heat treatment for crystallizing the ferroelectric film after performing the first heat treatment.   The step of performing the first heat treatment is performed under a condition where the temperature is 450 ° C. or more and 550 ° C. or less in an atmosphere having an ozone concentration of 0.7% or more and 2.0% or less. The method for manufacturing a capacitive element according to claim 5. The capacitor lower electrode, the manufacturing method of the capacitor according to claim 5 or 6, characterized in that consisting of Ir film or IrO _x film.

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