JP2007103963A - Method for manufacturing ferroelectric capacitor, ferroelectric capacitor and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a method for manufacturing a ceramic film having excellent characteristics and a ceramic film obtained by the method; a method for manufacturing a ferroelectric capacitor allowing for enhancing a fatigue property by improving an interface between a ceramic film and an electrode; a ferroelectric capacitor obtained by the method; and a semiconductor device applied with the ceramic film or the ferroelectric capacitor. <P>SOLUTION: The method for manufacturing the ferroelectric capacitor includes steps of: forming a lower electrode 20 on a substrate 10; forming a lower alloy film 24 of a compound made of a first metal making up a complex oxide on the lower electrode 20 and a second metal making up the lower electrode 20, formed by heat treating a raw material 30 including a complex oxide in an atmosphere pressurized to two atmosphere or more and containing oxygen at a volume ratio of 10% or less at a temperature raising rate of 100°C/min or less; forming a ceramic film 40 in which the raw material 30 is crystallized on the lower alloy film 24; and forming an upper electrode 50 on the ceramic film 40. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a ferroelectric capacitor, a ferroelectric capacitor, and a semiconductor device.

  At present, as a ferroelectric film applied to a semiconductor device (for example, a ferroelectric memory (FeRAM)), a ferroelectric film having a perovskite structure (for example, PbZrTiO series) or a ferroelectric film having a layered perovskite structure ( For example, BiLaTiO system, BiTiO system, and SrBiTaO system) have been proposed.

  Pb and Bi contained in these ferroelectric film materials have high vapor pressure and are likely to volatilize at low temperatures. In the crystallization process of the ferroelectric film, since heat treatment is performed at a high temperature, Pb, Bi, etc. are combined with oxygen in the atmosphere necessary for crystallization of the ferroelectric substance and scattered. Undesirably affects the properties of the crystallized ferroelectric film.

In addition, since the lattice constant of the crystallized ferroelectric film does not necessarily match the lattice constant of the metal film used as the electrode material, when applied to a ferroelectric capacitor having an MIM (Metal-Insulator-Metal) structure. Distortion due to lattice mismatch occurs and the characteristics are likely to deteriorate. In order to eliminate such lattice mismatch, a capacitor structure in which an alloy film is formed between a ferroelectric film and an electrode has been proposed (see Patent Document 1).
International Publication No. 00/17929 Pamphlet

  An object of the present invention is to provide a ferroelectric capacitor manufacturing method capable of improving the fatigue characteristics by improving the interface between the ceramic film and the electrode, and a ferroelectric capacitor obtained by this manufacturing method. It is in.

  Another object of the present invention is to provide a semiconductor device to which the ceramic film or the ferroelectric capacitor of the present invention is applied.

1. Manufacturing method of ceramic film (A) The first manufacturing method of the ceramic film of the present invention is as follows:
It includes crystallizing the raw material body containing the composite oxide by heat treatment in an atmosphere containing oxygen having a volume ratio of 10% or less under a pressure of 2 atm or higher.

  According to the present invention, vapor generation of a metal material (for example, Pb, Bi, etc.) contained in the raw material body is suppressed by a pressurized state of 2 atm or more, and oxygen contained in the atmosphere is 10% or less in volume ratio. By doing so, the bond between these metal materials and oxygen can be suppressed, and a ceramic film having a good crystal state can be obtained.

(B) The second method for producing a ceramic film of the present invention comprises:
It includes crystallizing the raw material body containing the composite oxide by heat treatment using a rapid thermal annealing method in a state where the raw material body is pressurized to 2 atm or more.

  Also according to the present invention, generation of vapor of a metal material (for example, Pb, Bi, etc.) contained in the raw material body accompanying a high-temperature heat treatment can be suppressed by a pressurized state of 2 atmospheres or more.

  Further, in the ferroelectric film, when the temperature is raised at a low speed in the heat treatment in crystallization, the initial crystal nuclei are generated at various angles, so that the crystal plane is likely to be randomly oriented. Therefore, in the present invention, a ceramic film having high crystal orientation can be obtained by performing heat treatment using a rapid thermal annealing method in which rapid heating is performed at several tens of degrees centigrade / second or more.

  Also in the second method for producing a ceramic film of the present invention, the heat treatment is performed in an atmosphere containing oxygen having a volume ratio of 10% or less, thereby suppressing the bond between the metal material contained in the raw material body and oxygen. Thus, a ceramic film having a better crystalline state can be obtained.

2. Method for Manufacturing Ferroelectric Capacitor (A) The first method for manufacturing a ferroelectric capacitor of the present invention is as follows.
Forming a lower electrode on the substrate;
The lower electrode is subjected to heat treatment in an atmosphere containing oxygen having a volume ratio of 10% or less and a temperature increase rate of 100 ° C./min or less by pressurizing the raw material body containing the composite oxide to 2 atm or more. A lower alloy film made of a compound of a first metal constituting the composite oxide and a second metal constituting the lower electrode is formed on the upper alloy film, and the raw material body is crystallized on the lower alloy film. Forming a ceramic film,
Forming an upper electrode on the ceramic film.

  In the present invention, the first metal is a metal contained in a complex oxide serving as a ferroelectric, and in the case of a ferroelectric film having a perovskite structure, for example, Pb, Zr, Ti, etc. may be mentioned. In the case of a ferroelectric film having a perovskite structure, for example, Bi, La, Ti, Sr, Ta and the like can be mentioned, but the invention is not limited thereto.

  In the present invention, the second metal is selected from known substances used as electrode materials for ferroelectric capacitors. For example, Pt, Ir, Al, Au, Ag, Ru, Sr, and the like are selected. Examples include, but are not limited to, conductive oxides or conductive nitrides contained in the constituent elements.

  According to the present invention, vapor generation of a metal material (for example, Pb, Bi, etc.) contained in the raw material body is suppressed by a pressurized state of 2 atm or more, and oxygen contained in the atmosphere is 10% or less in volume ratio. By doing so, the bond between these metal materials and oxygen can be suppressed, and a ceramic film having a good crystal state can be obtained.

  Furthermore, in the present invention, by setting the rate of temperature increase in the heat treatment to 100 ° C./min or less, the lower alloy film that is easily lattice-matched with both the lower electrode and the ceramic film in a relatively low temperature region in the temperature increase process of the heat treatment. The ceramic film is crystallized while producing. As a result, lattice distortion due to lattice mismatch between the lower electrode and the ceramic film is alleviated, and the interface between the layers becomes favorable, so that a ceramic film having a good crystal state with less distortion can be obtained.

  Therefore, according to the manufacturing method of the present invention, since the interface between each layer and the crystal state of the ceramic film are good, the polarization characteristics and fatigue characteristics of the ferroelectric capacitor can be improved.

(B) The second method for manufacturing a ferroelectric capacitor of the present invention is as follows.
Forming a lower electrode on the substrate;
Forming an oxide film of a first metal constituting a composite oxide on the lower electrode;
Forming a lower alloy film made of a compound of the first metal and the second metal constituting the lower electrode by subjecting the oxide film to a first heat treatment in a state of being pressurized to 2 atm or more;
The raw material body containing the composite oxide was crystallized on the lower alloy film by performing a second heat treatment using a rapid thermal annealing method in a state where the raw material body was pressurized to 2 atm or more. Forming a ceramic film,
Forming an upper electrode on the ceramic film.

  In the present invention, the first metal and the second metal are synonymous with those in the manufacturing method of the first ferroelectric capacitor.

  According to the present invention, the oxide film of the first metal constituting the complex oxide is formed on the lower electrode, and the lower alloy film made of the compound with the second metal constituting the lower electrode is formed by the first heat treatment. Generate. Since this lower alloy film is easily lattice-matched with both the lower electrode and the ceramic film, the lattice distortion due to the lattice mismatch between the lower electrode and the ceramic film is alleviated, and the interface between each layer is improved, and the distortion is reduced. A ceramic film having a good crystalline state with few is obtained.

  Furthermore, in the present invention, the second heat treatment is performed using a rapid thermal annealing method in which rapid heating is performed at several tens of degrees centigrade / second or more in a state where the raw material body including the composite oxide is pressurized to 2 atm or more. By doing so, it is possible to suppress generation of vapor of a metal material (for example, Pb, Bi, etc.) contained in the raw material body and to obtain a ceramic film having a good crystal state oriented in a desired crystal plane.

  Therefore, according to the manufacturing method of the present invention, since the interface between each layer and the crystal state of the ceramic film are good, the polarization characteristics and fatigue characteristics of the ferroelectric capacitor can be improved.

  In the second method for manufacturing a ferroelectric capacitor according to the present invention, the second heat treatment is performed in an atmosphere containing oxygen having a volume ratio of 10% or less, thereby bonding the metal material and oxygen contained in the raw material body. Thus, it is possible to obtain a ceramic film having a better crystalline state and to improve the characteristics of the ferroelectric capacitor.

  Furthermore, in the first and second ferroelectric capacitor manufacturing methods of the present invention, before the upper electrode is formed on the ceramic film, the third metal constituting the upper electrode on the ceramic film. Forming an upper alloy film made of a compound of the first metal and the third metal by heat-treating the oxide film under a pressure of 2 atm or more. The upper electrode can be formed on the upper alloy film.

  According to this aspect, since the lattice distortion between the layers is relaxed by the upper alloy film even at the interface between the ceramic film and the upper electrode, a ferroelectric capacitor having good characteristics can be obtained. Further, since the heat treatment for generating the upper alloy film is performed in a state of being pressurized to 2 atm or more, a metal material (for example, Pb, Bi, etc.) contained in the composite oxide from the surface of the ceramic film. Generation of steam can be suppressed.

(C) The third method for manufacturing a ferroelectric capacitor of the present invention is as follows.
Forming at least a lower electrode, a ceramic film, and an upper electrode on the substrate;
After at least the upper electrode is formed, a heat treatment for recovering the ferroelectric characteristics is performed in a state where the pressure is increased to 2 atmospheres or more.

  In the third method for manufacturing a ferroelectric capacitor according to the present invention, after a ferroelectric capacitor structure is formed on a substrate, heat treatment is performed in a state of being pressurized to 2 atm or more as post-annealing, and thereby the ceramic film and The interface state between the upper electrode and the lower electrode is improved, and the ferroelectric characteristics can be recovered. In this manufacturing method, the heat treatment can be performed using a rapid thermal annealing method.

(D) A fourth method for manufacturing a ferroelectric capacitor according to the present invention includes:
Forming at least a lower electrode, a ceramic film, and an upper electrode on the substrate;
It includes performing a heat treatment for recovering the ferroelectric characteristics in a state where the ceramic film is etched to a given shape at least and then pressurized to 2 atm or more.

  In the fourth method of manufacturing a ferroelectric capacitor according to the present invention, at least after the ceramic film is etched, heat treatment is performed in a state of being pressurized to 2 atm or more as post-annealing, thereby recovering process damage in the etching process. Can be made. In this manufacturing method, the heat treatment can be performed using a rapid thermal annealing method.

  The ceramic film manufacturing method and the ferroelectric capacitor manufacturing method of the present invention can take at least the following aspects.

  (A) In the heat treatment for crystallizing the raw material body, it is possible to pressurize at least 2 atmospheres before raising the temperature.

  According to this aspect, by increasing the pressure in the atmosphere in the crystallization process before raising the temperature, vapor generation of the metal material (for example, Pb, Bi, etc.) contained in the complex oxide in the low temperature region of the heat treatment is performed. It can be effectively suppressed.

  (B) The composite oxide contains Pb as a constituent element, and in the heat treatment for crystallizing the raw material body, the temperature is further increased after pressurizing at least 100 ° C. to 2 atm or higher in the temperature increasing process. It can be carried out.

  According to such an aspect, by pressurizing to 2 atm or more in a low temperature region of 100 ° C. or lower in the temperature rising process of the heat treatment, Pb is contained in the raw material body of the composite oxide containing Pb by the subsequent temperature rising. The effect of preventing generation of steam by combining with oxygen in the atmosphere can be further ensured.

  (C) The temperature raising process of the heat treatment for crystallizing the raw material body can be performed in a pressurized state with respect to the atmospheric pressure, and the temperature lowering process of the heat treatment can be performed in a reduced pressure state with respect to the pressurized state. .

  According to this aspect, in the temperature rising process, the metal material is prevented from being detached from the raw material body by pressurization, and in the temperature lowering process, the surplus material contained in the atmosphere by reducing the pressure from the pressurized state. Such an impurity can be prevented from adhering to the ceramic film.

  (D) The raw material body is a mixture of a sol-gel raw material containing at least one of the hydrolyzate and polycondensate of the composite oxide and a MOD raw material containing a constituent element of the composite oxide in an organic solvent. be able to.

  The complex oxides that make up ferroelectrics contain metal materials (eg, Pb, Bi, etc.) that are liable to generate vapor in the low temperature region, so these materials are excessive for crystallization with high temperature processing. It is often added to.

  According to this aspect, the raw material body is constituted by a mixture of the sol-gel raw material in which the constituent elements of the composite oxide are bonded by hydrolysis or polycondensation and the MOD raw material in which each constituent element can move relatively freely in the solvent. By doing so, since both raw materials function complementarily in the crystallization process of the raw material body, excessive additives in the raw material body can be reduced, and a ceramic film having a good surface morphology can be generated.

  (E) In addition to the composite oxide, the raw material body may include a paraelectric material having a catalytic action on the composite oxide.

  According to this aspect, in addition to the composite oxide constituting the ferroelectric material in the raw material body, the paraelectric material is mixed, so that in the crystallization process of the composite oxide, some constituent elements of the composite oxide However, the crystallization temperature can be lowered by substituting with the constituent elements of the paraelectric material.

  As such a paraelectric material, for example, an oxide containing Si or Ge in the constituent elements, or an oxide containing Si and Ge in the constituent elements can be adopted.

3. Ceramic film, ferroelectric capacitor, semiconductor device (A) The ceramic film of the present invention is obtained by the method for producing a ceramic film of the present invention.

  (B) The ferroelectric capacitor of the present invention can be obtained by the method for manufacturing a ferroelectric capacitor of the present invention.

  (C) The first semiconductor device of the present invention has the ceramic film of the present invention as a gate insulating film.

  (D) The second semiconductor device of the present invention includes the ferroelectric capacitor of the present invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1A to FIG. 1E are cross-sectional views schematically showing a manufacturing process of a ferroelectric capacitor according to this embodiment.

First, as shown in FIG. 1A, the lower electrode 20 is formed on the substrate 10. The lower electrode 20 is made of, for example, a metal such as Pt, Ir, Al, Au, Ag, Ru, or Sr, an oxide conductor (such as IrO _x ), a nitride conductor (such as TiN), or the like. It can be formed using a sputtering method as a material. The lower electrode 20 may be a single layer film or a laminated multilayer film.

  Next, as shown in FIG. 1B, a raw material body 30 containing a complex oxide is formed on the lower electrode 20. Examples of a method for forming the raw material body 30 include a coating method and an LSMCD method. Examples of the coating method include a spin coating method and a dipping method. The raw material body 30 includes a sol-gel raw material and a MOD raw material. As the sol-gel raw material, a raw material having a lower crystallization temperature and a higher crystal nucleus formation rate and crystal growth rate than the MOD raw material is selected.

  Specifically, the sol-gel raw material can be adjusted as follows. First, a metal alkoxide having 4 or less carbon atoms is mixed and subjected to hydrolysis and polycondensation. By this hydrolysis and polycondensation, a strong bond of M-O-M-O ... can be formed. The M-O-M bond obtained at this time has a structure close to the crystal structure (perovskite structure) of ceramics. Here, M is a metal element (for example, Bi, Ti, La, Pb, etc.), and O represents oxygen. Next, a solvent is added to the product obtained by performing hydrolysis and polycondensation to obtain a raw material. Thus, the sol-gel raw material can be adjusted.

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

  Further, in the raw material body 30, the sol-gel raw material and the MOD raw material are adjusted to the stoichiometric composition of the composite oxide, respectively, and a metal material (for example, Pb, Bi) contained in the composite oxide is included in these mixtures. Can be included in excess of at least 5% with respect to the stoichiometric composition. For example, metal materials such as Pb and Bi are combined with oxygen at a low temperature to generate steam. Therefore, in order to make up for the shortage in the crystallization process, conventionally, 10% to 20% of Pb or Bi is used as an excessive additive as a raw material. It was included in the body 30. However, the excess additive remaining after crystallization can enter between the crystals of the ceramic film 40 or between the crystal and the electrode, and can also cause deterioration in crystal quality.

  Therefore, in the manufacturing method of the present embodiment, the sol-gel raw material in which the element arrangement is close to the crystal and the MOD raw material in which the constituent elements easily move are mixed in advance, so that both raw materials complement each other during crystallization. Functionally, excess additives such as Pb and Bi can be reduced as much as possible, specifically 5% or less of the stoichiometric composition. This prevents excessive additives such as Pb and Bi remaining after the crystallization of the raw material body 30 from entering between the crystals and between the lower electrode 20 and the crystals and generating a deteriorated layer. be able to.

  In addition to the composite oxide, a paraelectric material having a catalytic action on the composite oxide may be mixed in the raw material body 30. In addition to the composite oxide constituting the ferroelectric material in the raw material body 30, a paraelectric material is mixed, so that in the crystallization process of the composite oxide, some constituent elements of the composite oxide are paraelectric. The crystallization temperature can be lowered by substituting with the constituent elements of the material.

As such a paraelectric material, for example, an oxide containing Si or Ge in the constituent elements, or an oxide containing Si and Ge in the constituent elements can be adopted. The oxide is a paraelectric material represented by ABO _X or BO _X , and the A site is composed of any single element or complex element of Pb, Bi, Hf, Zr, V, and W, and the B site A material composed of a single element or a complex element of either Si or Ge can be used. Specifically, PbSiO-based _{(Pb 5 Si 3 O X,} Pb 2 Si 1 O X), PbGeO system _{(Pb 5 Ge 3 O X,} Pb 2 Ge 1 O X), BiSiO system _(Bi 4 _Si 3 _{O X} , Bi ₂ Si ₁ O _X ), BiGeO-based (Bi ₄ Ge ₃ O _X , Bi ₂ Si ₁ O _X ), ZrGeO _X , HfGeO _X , VgeO _X , WGeO _X , VSiO _X , WSiO _{X and the} like. When Zr, Hf, V, and W are used for the A site, there is an effect of suppressing oxygen deficiency in the ferroelectric.

  Next, if necessary, the raw material body 30 is dried and temporarily fired.

  Next, as shown in FIGS. 1C and 1D, the raw material body 30 is heat-treated to crystallize the raw material body 30 to form the ceramic film 40. In general, the sol-gel raw material has a lower crystallization temperature than the MOD raw material. The sol-gel raw material has a higher crystal nucleus formation rate and crystal growth rate than the MOD raw material. Therefore, in the crystallization process of the raw material body 30 which is a mixture of these, the crystallization of the sol-gel raw material proceeds prior to the crystallization of the MOD raw material, so that the MOD raw material remains in the gap between the crystal nuclei formed by the sol-gel raw material. It will be. Then, crystallization of the MOD raw material proceeds independently in the gap between the crystal nuclei of the sol-gel raw material, and the gap is filled. The sol-gel raw material and the MOD raw material differ in the direction in which crystals are easily oriented. Therefore, in the crystallization process of both raw materials, the growth is blocked and a fine crystal grows. As a result, the formed ceramic film 40 has good surface morphology.

  Further, in the manufacturing method of the present embodiment, a pressurized state of 2 atm or more is set in a low temperature region of 100 ° C. or lower in the temperature rising process of the heat treatment. This is because, for example, in a PbZrTiO-based (hereinafter referred to as PZT) composite oxide, it is known that Pb binds to oxygen at a relatively low temperature and is easily scattered in the atmosphere (Electrochemical Handbook 4th Edition). 128, Maruzen, published in 1985), which is intended to prevent the metal material from scattering into the atmosphere. In this heat treatment, a pressurized state of 2 atm or more may be applied before the temperature rise.

  In this embodiment mode, since the heat treatment is performed in an atmosphere containing oxygen with a volume ratio of 10% or less, the metal material can be prevented from being desorbed in combination with oxygen. It is possible to further enhance the effect of preventing scattering.

  Further, in such heat treatment, the temperature raising process can be performed in a pressurized state with respect to the atmospheric pressure as described above, and the temperature lowering process can be performed in a reduced pressure state with respect to the pressurized state. This prevents the metal material from being detached from the raw material body by pressurization during the temperature rising process, and impurities such as surplus materials contained in the atmosphere by reducing the pressure from the pressurized state during the temperature lowering process. Can be prevented from adhering to the ceramic film and the generation of a deteriorated layer in the ceramic film.

  Note that the method of the present embodiment includes Bi that is easily bonded to oxygen in the low temperature region and diffuses into the atmosphere in the same manner as Pb, for example, BiLaTiO (hereinafter referred to as BLT), BiTiO (hereinafter referred to as BIT). And SrBiTaO-based (hereinafter referred to as SBT) composite oxides.

  Further, in the heat treatment, the lower alloy film 24 can be formed between the lower electrode 20 and the ceramic film 40 in the temperature rising process. The lower alloy film 24 is made of an alloy of a metal element constituting the lower electrode 20 and a metal element contained in the raw material body 30. At this time, an additive of a metal material such as Pb or Bi excessively contained in the raw material body 30 with respect to the stoichiometric composition of the composite oxide becomes a material of the lower alloy film 24.

Here, for example, in PZT, when Pt is selected as the material of the lower electrode 20, the lattice constant (a, b, c: 3.96) of the lower electrode 20 and the lattice constant (a, b: 4.04, c: 4.14) does not match, and distortion due to lattice mismatch occurs at the interface. Since this distortion affects the fatigue characteristics of the ferroelectric capacitor, it is desirable to reduce it as much as possible. PbPt ₃ (a, b, c: 4.05) is an example of a substance having a lattice constant close to that of the PZT ceramic film 40. As alloy compounds composed of Pb and Pt, in addition to PbPt ₃ , PbPt (a, b: 4.24, c: 5.48), Pb ₂ Pt (a, b: 6.934, c: 5.764), Pb ₄ Pt (a, b: 6.64, c: 5.97) are considered, but the lattice constant (a, b, c: 4.05) of PbPt ₃ is the same as that of the PZT ceramic film 40 (a, b: 4.04, c: 4.14). Since there are few mismatches, it is suitable as the lower alloy film 24. In view of this, Pb suitable for the lower alloy film 24 needs to have a high valence, and Pb oxides PbO ₂ and Pb ₃ O ₄ having a high valence have a crystallization temperature of the raw material body 30. On the other hand, it tends to be steam at low temperatures. That is, the production process of the lower alloy film 24 needs to be performed in a low temperature region in order to effectively use a metal material having a high valence.

  Therefore, in the heat treatment of the present embodiment, the lower electrode is formed at a low temperature range of about 100 ° C. to 200 ° C. as shown in FIG. A lower alloy film 24 is formed between 20 and the raw material body 30 being crystallized. Due to the presence of the lower alloy film 24, distortion due to lattice mismatch at the interface between the layers is alleviated, the surface morphology of the crystallized ceramic film 40 is improved, and the fatigue characteristics of the finally manufactured ferroelectric capacitor It contributes to the improvement.

  In this heat treatment, the raw material body 30 is crystallized by further raising the temperature through the formation process of the lower alloy film 24, and the ceramic film 40 is formed on the lower alloy film 24.

  As described above, in the method of manufacturing the ferroelectric capacitor according to the present embodiment, the lower alloy film 24 is formed in which the heat treatment for crystallization of the raw material body 30 improves the lattice mismatch at the interface between the ceramic film 40 and the lower electrode 20. It is characterized by a process.

  Finally, as shown in FIG. 1E, the upper electrode 50 is formed on the ceramic film 40 to obtain a ferroelectric capacitor. The material and forming method of the upper electrode 50 can be the same as those of the lower electrode 20.

  As described above, according to the method for manufacturing a ferroelectric capacitor in accordance with the present embodiment, it is possible to prevent desorption of the complex oxide material into the atmosphere by heat treatment in a pressurized state and a low oxygen state. it can. Furthermore, since the lower alloy film 24 can be formed in the low temperature region of the temperature raising process of the heat treatment, the lower alloy film 24 can relieve the distortion at the interface of the ceramic film 40 and improve the surface morphology. In addition, the electrical characteristics of the capacitor can be improved.

  In the method for manufacturing a ferroelectric capacitor according to the present embodiment, after forming each layer up to the upper electrode 50 on the substrate 10, the ferroelectric characteristics are exhibited in a state of being pressurized to 2 atm or more as post-annealing. Heat treatment for recovery can be performed. As a result, the interface state between the ceramic film 40 and the upper electrode 50 and the lower electrode 20 is improved, and the ferroelectric characteristics can be recovered.

  Furthermore, in the method for manufacturing a ferroelectric capacitor according to the present embodiment, after forming each layer up to the upper electrode 50 on the substrate 10, the ferroelectric capacitor is patterned by etching or the like, and then post-annealed to 2 atm or more. A heat treatment can be performed to restore the ferroelectric properties in a pressurized state. Thereby, the process damage in the etching process can be recovered.

  In addition, these post-annealing may be performed slowly using FA (furnace), or may be performed rapidly using a rapid thermal annealing method.

  Note that the various heat treatments described above can be performed in an atmosphere inert to the vapor generation of the metal material constituting the composite oxide, such as nitrogen, argon, or xenon. By performing the heat treatment in such an atmosphere, the effect of suppressing vapor generation of the metal material constituting the composite oxide is further enhanced.

  In addition, a plurality of stages of pressurization can be performed in at least one of the temperature increasing process and the temperature decreasing process of the various heat treatments described above.

  Hereinafter, more detailed examples of the manufacturing method according to the present embodiment will be described with reference to the drawings.

Example 1
In this example, a study was conducted by forming a film of Pb (Zr _0.35 , Ti _0.65 ) O ₃ on a given substrate on which a Pt electrode was formed by using a spin coating method.

In this example, a raw material in which Pb was added to a mixture of a sol-gel solution and a MOD solution each adjusted to a stoichiometric composition of PZT (Zr / Ti = 35/65) so that the molar ratio was 5% excess. The solution was used. The Pb additive is used to form PbPt ₃ at the interface between the Pt electrode and the PZT film.

These raw material solutions were spin-coated (3000 rpm, 30 seconds), and the process of pre-baking the raw material solution at 400 ° C. for 5 minutes was repeated three times to form a 150 nm raw material body on the Pt electrode. Next, as shown in FIG. 2, the temperature is raised to 650 ° C. in an atmosphere containing oxygen at a volume ratio of 1% using FA (furnace), and a heat treatment for 30 minutes is performed. Then, the raw material body was crystallized to obtain a PZT film having a perovskite structure. In this temperature rising process, in order to form a PbPt ₃ film that is an alloy of Pt of the Pt electrode and Pb in the raw material body in a low temperature region of about 100 ° C. to 200 ° C., the temperature rising rate is set to 20 ° C./min. did.

FIG. 3 is a micrograph of the surface of the PZT film obtained at this time. According to this, it can be seen that fine crystals having an average particle diameter of about 50 nm are uniformly distributed and the surface morphology is good. This is because the lattice mismatch at the interface is reduced by the PbPt ₃ layer formed at the interface between the Pt electrode and the PZT film, and further, during the crystallization of the PZT film by the heat treatment performed under conditions of a pressurized state and a low oxygen state. This is thought to be due to the prevention of Pb desorption.

Moreover, the Raman scattering spectrum was measured about this PZT film | membrane. Further, for comparison with the prior art in this measurement, as shown in FIG. 4, a crystal is obtained by performing a heat treatment by a rapid thermal annealing method (hereinafter, “conventional method 1”) in the atmosphere without applying pressure. Measurement was also performed on the Raman scattering spectrum of the converted PZT film. Then, as shown in FIGS. 5A and 5B, the PZT film according to the manufacturing method of this example and the PZT film according to the conventional method 1 have 500 R / cm ^{−1 to} 700 R / cm ⁻¹ . There is a difference in spectral shape. This is because a heterogeneous phase is generated in the PZT film according to the conventional method 1. Figure 5 (C) is an enlarged view of the spectral shape of ^500R / ^{cm -1 ~700R} / cm -1 in the measurement results of the PZT film by the conventional method 1. It can be seen that the PZT film according to the conventional method 1 has a peak indicating the generation of a heterogeneous phase of PZT or an altered layer, as shown in FIG. The reason why such a significant difference is seen is considered to be due to the large effect of reducing the composition variation in the PZT crystallization process by suppressing the vapor generation of Pb by the heat treatment in the pressurized and low oxygen state.

  Next, in this example, a Pt electrode is formed on the crystallized PZT film as an upper electrode, and then post-annealing is performed in a state where the pressure is increased to 2 atm to produce a ferroelectric capacitor. Body characteristics were evaluated.

FIG. 6 shows the hysteresis characteristics of the ferroelectric capacitor obtained by the manufacturing method of this example. As shown in FIG. 6, in the ferroelectric capacitor of this example, a hysteresis shape with good squareness that saturates at a low voltage of 2 V or less was obtained. Further, it was found that this ferroelectric capacitor had a polarization value Pr of about 30 μC / cm ² and exhibited good polarization characteristics.

Next, the fatigue characteristics of the ferroelectric capacitor obtained by the manufacturing method of this example and the ferroelectric capacitor in which the upper electrode was formed on the PZT film obtained by the manufacturing method of the conventional method 1 were examined. It was. FIGS. 7 (A) and 7 (B), relative to those of the ferroelectric capacitor, 2V, after giving 10 times the triangular wave pulses of 66 Hz, 1.5V, more than 10 ⁸ times 500kHz of the square-wave pulse It is a figure which shows the hysteresis characteristic before and behind the fatigue test which gave the polarization reversal. FIG. 7A shows a capacitor obtained by the manufacturing method of this example, and FIG. 7B shows a capacitor obtained by the conventional method 1. FIG. According to FIG. 7A, in the capacitor obtained by this example, no change in the hysteresis shape is observed before and after the test. On the other hand, according to FIG. 7B, it can be seen that in the capacitor obtained by the conventional method 1, the polarization characteristics are degraded in the hysteresis shape after the test. This indicates that the distortion due to lattice mismatch is mitigated at the lower electrode side interface of the PZT film because the manufacturing method of the present example involves the formation process of the PbPt ₃ alloy film in the crystallization process of the PZT film. ing.

  As described above, in the manufacturing method of the present embodiment, the ceramic film has a good surface morphology due to the pressure in the crystallization process of the ceramic film and the heat treatment accompanying the lower alloy film forming process in the low oxygen state, It was confirmed that the ferroelectric capacitor including this has good hysteresis characteristics and fatigue characteristics.

(Example 2)
In this example, in addition to the case where the raw material solution is a mixture of a sol-gel solution and a MOD solution, as a comparative example, the sol-gel solution alone or the MOD solution alone is used by using a spin coating method on the Pt electrode. The characteristics of the formed PZT film were examined. Each raw material solution was prepared by adding Pb so that the molar ratio was 5% excess to those adjusted to the stoichiometric composition of PZT (Zr / Ti = 35/65). In the heat treatment for crystallization, the raw material body to which each raw material solution is applied is pressurized to 2 atm using FA and heated to 650 ° C. in an atmosphere containing 1% by volume of oxygen. For 30 minutes.

  8A to 8C are photomicrographs obtained by observing the surface of the PZT film obtained in this example. 8A shows a PZT film using only a MOD solution as a raw material solution, FIG. 8B shows a PZT film using a mixture of a sol-gel solution and a MOD solution as a raw material solution, and FIG. The surface morphology of a PZT film using only a sol-gel solution as a raw material solution is shown.

  In the micrographs shown in FIGS. 8 (A) to 8 (C), the particle size is smaller when the mixture of the sol-gel solution and the MOD solution is used than when only the MOD solution and only the sol-gel solution are used. It can be seen that the surface morphology is such that fine crystals are uniformly distributed.

  Further, in this example, for a PZT film using a mixture of a sol-gel solution and a MOD solution as a raw material solution, the mixing ratio of the sol-gel solution and the MOD solution is 2: 1, 1: 1, 1: 2 in molar ratio. The characteristics of the PZT film obtained when changed were investigated.

  FIG. 9A to FIG. 9E are micrographs obtained by observing the surface of the PZT film obtained at this time. 9A and 9E show, as comparative examples of the PZT film of this example, a PZT film using only the sol-gel solution prepared above as a raw material solution, and only a MOD solution as a raw material solution. A micrograph of the PZT film is also shown.

  According to FIGS. 9A to 9E, the PZT film obtained by the mixture of the sol-gel solution and the MOD solution is obtained only from the sol-gel solution, whereas the average particle size is as small as 30 nm to 70 nm. It can be seen that the PZT film has an average particle diameter of 100 nm, and the PZT film obtained only from the MOD solution has an average particle diameter of 2 μm. That is, the case where the mixture of the sol-gel solution and the MOD solution is used has a good surface morphology in which fine crystals are uniformly distributed as compared with the case where only the sol-gel solution or only the MOD solution is used. This is because, in the case of only the sol-gel solution and the case of only the MOD solution, the generation density of the initial crystal nuclei is different, but since the crystallization proceeds according to the initial crystal nuclei, the crystal grain size increases. It is considered a thing. However, when a mixture of a sol-gel solution and a MOD solution is used, the initial crystal nuclei are formed with high density by the sol-gel solution, and the MOD solution is crystallized so as to fill the gap. It is considered to be.

  Next, the electrical characteristics of the ferroelectric capacitor having the upper electrode formed on each of the PZT films were examined. FIG. 10B to FIG. 10D are diagrams showing hysteresis characteristics of the ferroelectric capacitor obtained by this example. FIG. 10A is a diagram showing the hysteresis characteristics of the ferroelectric capacitor when only the sol-gel solution is used. FIG. 10E is a diagram showing hysteresis characteristics of the ferroelectric capacitor when only the MOD solution is used.

  10A to 10E, in a ferroelectric capacitor using a mixture of a sol-gel solution and a MOD solution as a raw material solution, only the sol-gel solution and only the MOD solution at any mixing ratio. As compared with a ferroelectric capacitor using as a raw material solution, a hysteresis shape with good squareness that is saturated at a low voltage of 2 V or less was obtained.

  Therefore, according to the present embodiment, the mixing ratio of the sol-gel solution and the MOD solution in the raw material solution can improve the surface morphology of the ceramic film in a molar ratio of 1: 2 to 2: 1. It was confirmed that a ferroelectric capacitor having a hysteresis shape with good squareness can be manufactured.

  Further, in this example, the temperature characteristics of a ferroelectric capacitor having a PZT film obtained from a mixture of sol-gel solution and MOD solution (mixing ratio 1: 1) were verified. The temperature characteristics are measured by measuring hysteresis characteristics in the range of 25 ° C. to 100 ° C., and the results are shown in FIGS. 11 (A) to 11 (D). According to FIGS. 11 (A) to 11 (D), the ferroelectric capacitor obtained by the manufacturing method of this example is good in that the hysteresis shape hardly changes even at a high temperature of 100 ° C. It was found to have a good temperature characteristic.

FIG. 12 is a plot of the polarization value Pr ² [(μC / cm ² ) ² ] normalized on the vertical axis and the temperature [° C.] on the horizontal axis based on these results. According to FIG. 12, in the ferroelectric capacitor having the PZT film manufactured by the conventional technique, the polarization value deteriorates as the temperature rises, whereas the ferroelectric capacitor having the PZT film manufactured by the method of this embodiment is used. The body capacitor showed a substantially constant polarization value with respect to the temperature change, and good temperature characteristics similar to those of the PZT bulk were obtained.

(Example 3)
In this example, the dependency of the Zr / Ti ratio in the raw material solution of Pr (Zr, Ti) O ₃ was verified. Specifically, in Examples 1 and 2 described above, a raw material solution having a Zr / Ti ratio of 35/65 was used, but in this example, a raw material solution having a Zr / Ti ratio of 20/80 was used. Comparison of electrical characteristics of ferroelectric capacitors having a PZT film produced when only a MOD solution was used as a raw material solution and a mixture of a sol-gel solution and a MOD solution (mixing ratio 1: 1) was used as a raw material solution went.

  FIG. 13A and FIG. 13B are diagrams showing the hysteresis characteristics of these ferroelectric capacitors. According to FIG. 13A and FIG. 13B, even when the Zr / Ti ratio is 20/80, when the mixture of the sol-gel solution and the MOD solution is used, only the MOD solution is used. Compared to the above, it becomes a hysteresis shape with good squareness that saturates at a low voltage. That is, according to this example, it can be confirmed that the production method using the mixture of the sol-gel solution and the MOD solution as the raw material solution is effective even when the Zr / Ti ratio is changed.

Example 4
In this example, in the manufacturing method described in Example 1 above, the influence on the electrical characteristics of the ferroelectric capacitor when the temperature of the heat treatment for crystallizing the PZT film is lowered to 580 ° C. and 425 ° C. Verified.

  FIGS. 14A and 14B are diagrams showing hysteresis characteristics of a ferroelectric capacitor having a PZT film crystallized by heat treatment at 580 ° C. and 425 ° C. FIG. According to FIGS. 14A and 14B, it was found that a ferroelectric capacitor having a hysteresis characteristic sufficiently reaching a practical level can be obtained even when the crystallization temperature is lowered.

[Second Embodiment]
FIG. 15 is a cross-sectional view schematically showing the manufacturing process of the ferroelectric capacitor according to the present embodiment. Note that members having substantially the same functions as those in FIG. 1 described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the method for manufacturing a ferroelectric capacitor according to the present embodiment, a process for forming an alloy film is separately provided on the upper and lower interfaces of the ceramic film to improve the fatigue characteristics of the ferroelectric capacitor and to crystallize the ceramic film. The crystal orientation of the ceramic film was improved by heat treatment using rapid thermal annealing.

In the manufacturing process of the present embodiment, first, as shown in FIG. 15A, the lower electrode 20 is formed on the substrate 10, and subsequently, a composite oxide (for example, PZT) is formed on the lower electrode 20. , BIT, BLT, SBT, etc.), an oxide film 22 containing an oxide (eg, PbO ₂ , BiO _2, etc.) of a metal material (eg, Pb, Bi, etc.) is formed.

  Next, as shown in FIG. 15B, heat treatment is performed in a state where the oxide film 22 is pressurized to 2 atm or more, and the metal material (for example, Pt, Ir, etc.) of the lower electrode 20 and the composite oxidation are performed. A lower alloy film 24 made of a compound with a metal material (for example, Pb, Bi, etc.) constituting the object is formed. The heat treatment for forming the lower alloy film 24 is performed at a lower temperature than the heat treatment for crystallization of the ceramic film 40 described later in order to prevent the metal material constituting the composite oxide from scattering into the atmosphere. Done in

  Next, as shown in FIG. 15C, a raw material body 30 is formed on the lower alloy film 24. This raw material body 30 can also contain a sol-gel raw material and a MOD raw material, as in the case of the first embodiment. Further, in the raw material body 30, the sol-gel raw material and the MOD raw material are adjusted to the stoichiometric composition of the composite oxide, respectively, and the mixture thereof has a composite oxidation of 5% or less with respect to the stoichiometric composition. It is desirable that the metal material (for example, Pb, Bi) contained in the object is excessively contained. In the manufacturing method of this embodiment, since the lower alloy film 24 is formed before the raw material body 30 is formed, the metal material contained in the composite oxide does not need to be excessively added to the raw material body 30.

  In addition to the composite oxide, a paraelectric material having a catalytic action on the composite oxide may be mixed in the raw material body 30. In addition to the composite oxide constituting the ferroelectric material in the raw material body 30, a paraelectric material is mixed, so that in the crystallization process of the composite oxide, some constituent elements of the composite oxide are paraelectric. The crystallization temperature can be lowered by substituting with the constituent elements of the material.

  As such a paraelectric material, for example, an oxide containing Si or Ge in the constituent elements, or an oxide containing Si and Ge in the constituent elements can be adopted.

  Next, as shown in FIG. 15D, a heat treatment for crystallizing the raw material body 30 is performed to form a ceramic film 40 made of the composite oxide. This heat treatment is performed using a rapid thermal annealing method in which rapid heating is performed at a heating rate of several tens of degrees centigrade / second. In the crystallization process of the composite oxide, when the temperature rising rate is lowered, initial crystal nuclei are formed at various angles, and the crystals of the ceramic film are easily oriented randomly. However, when rapid heating is performed by the rapid thermal annealing method as in this embodiment, a high-quality crystal film having excellent orientation can be obtained.

  Further, in the heat treatment for crystallization, a pressurized state of 2 atm or more is set in a low temperature region of 100 ° C. or lower in the temperature rising process. This is to prevent, for example, metal materials such as Pb and Bi that are likely to be generated at a relatively low temperature from being scattered in the atmosphere before crystallization. In this heat treatment, a pressurized state of 2 atm or more may be applied before the temperature rise.

  In this embodiment mode, since the heat treatment is performed in an atmosphere containing oxygen with a volume ratio of 10% or less, the metal material can be prevented from being desorbed in combination with oxygen. It is possible to further enhance the effect of preventing scattering.

  Further, in such heat treatment, the temperature raising process can be performed in a pressurized state with respect to the atmospheric pressure as described above, and the temperature lowering process can be performed in a reduced pressure state with respect to the pressurized state. This prevents the metal material from being detached from the raw material body by pressurization during the temperature rising process, and impurities such as surplus materials contained in the atmosphere by reducing the pressure from the pressurized state during the temperature lowering process. Can be prevented from adhering to the ceramic film and the generation of a deteriorated layer in the ceramic film.

  Also in the present embodiment, when the raw material body 30 includes the sol-gel raw material and the MOD raw material, in the crystallization process of both raw materials, the growth is interrupted and a fine crystal grows. As a result, the ceramic film 40 formed by crystallization has good surface morphology.

Next, as shown in FIG. 15E, oxidation of a metal material (for example, Pb, Bi, etc.) constituting a composite oxide (for example, PZT, BIT, BLT, SBT, etc.) on the ceramic film 40. An oxide film 42 containing a material (eg, PbO ₂ , BiO _2, etc.) is formed. Then, an upper electrode 50 is further formed on the oxide film 42. The oxide film 42 is formed in order to form an alloy film at the interface between the ceramic film 40 and the upper electrode 50.

  Next, as shown in FIG. 15F, a heat treatment is performed on these stacked bodies at a pressure of 2 atm or higher, so that a metal material (for example, composite oxide) included in the oxide film 42 (for example, , Pb, Bi, etc.) and an upper alloy film 44 made of an alloy of a metal material (for example, Pt, Ir, etc.) of the upper electrode 50 is formed. This upper alloy film 42 also has a role similar to that of the lower alloy film 22 described above, and alleviates distortion due to lattice mismatch between the ceramic film 40 and the upper electrode 50, thereby improving the surface morphology of the ceramic film 40. The fatigue characteristics of the ferroelectric capacitor can be improved.

  As described above, according to the method for manufacturing a ferroelectric capacitor in accordance with the present embodiment, it is possible to prevent desorption of the complex oxide material into the atmosphere by heat treatment in a pressurized state and a low oxygen state. it can. Further, since the heat treatment in crystallization is performed by a rapid thermal annealing method, a ferroelectric capacitor having a high quality ceramic film excellent in crystal orientation can be obtained by rapid heating. Furthermore, by introducing heat treatment for forming the lower alloy film 24 and the upper alloy film 44, the lower alloy film 24 and the upper alloy film 44 alleviate the distortion at the interface of the ceramic film 40, and the surface morphology is improved. It is possible to improve the electrical characteristics of the capacitor.

  In the method for manufacturing a ferroelectric capacitor according to the present embodiment, after forming each layer up to the upper electrode 50 on the substrate 10, the ferroelectric characteristics are exhibited in a state of being pressurized to 2 atm or more as post-annealing. Heat treatment for recovery can be performed. As a result, the interface state between the ceramic film 40 and the upper electrode 50 and the lower electrode 20 is improved, and the ferroelectric characteristics can be recovered.

  Furthermore, in the method for manufacturing a ferroelectric capacitor according to the present embodiment, after forming each layer up to the upper electrode 50 on the substrate 10, the ferroelectric capacitor is patterned by etching or the like, and then post-annealed to 2 atm or more. A heat treatment can be performed to restore the ferroelectric properties in a pressurized state. Thereby, the process damage in the etching process can be recovered.

  In addition, these post-annealing may be performed slowly using FA (furnace), or may be performed rapidly using a rapid thermal annealing method.

  Note that the various heat treatments described above can be performed in an atmosphere inert to the vapor generation of the metal material constituting the composite oxide, such as nitrogen, argon, or xenon. By performing the heat treatment in such an atmosphere, the effect of suppressing vapor generation of the metal material constituting the composite oxide is further enhanced.

  In addition, a plurality of stages of pressurization can be performed in at least one of the temperature increasing process and the temperature decreasing process of the various heat treatments described above.

  Hereinafter, more detailed examples of the manufacturing method according to the present embodiment will be described with reference to the drawings.

(Example)
In this example, a ferroelectric capacitor having a composite oxide made of Pb (Zr _0.35 , Ti _0.65 ) O ₃ as a ceramic film on a given substrate on which a Pt electrode was formed was examined. .

First, a 0.1 wt% PbO ₂ forming sol-gel solution was spin-coated on a Pt electrode (3000 rpm, 30 seconds), and this was pressurized to 9.9 atm as shown in FIG. In addition, a first heat treatment was performed at 150 ° C. for 120 minutes in a nitrogen atmosphere to form a PbPt ₃ film, which is an alloy of Pb, which is a metal material of a composite oxide, and a Pt electrode, which is a lower electrode, on a Pt electrode. .

Next, a sol-gel solution of PZT (Zr / Ti = 35/65) adjusted to a stoichiometric composition was spin-coated (3000 rpm, 30 seconds) on the PbPt ₃ film, and the sol-gel solution was then applied at 400 ° C. for 5 minutes. The pre-baking step was repeated three times to form a 150 nm raw material body on the Pt electrode.

  Subsequently, as shown in FIG. 16, in an atmosphere pressurized to 9.9 atm and containing 1% by volume of oxygen, the temperature is rapidly raised to 650 ° C. at a temperature raising rate of 100 ° C./second, A second heat treatment was performed at 650 ° C. for 10 minutes to crystallize the raw material body, thereby forming a PZT film having a perovskite structure.

Thereafter, a 0.1 wt% PbO ₂ forming sol-gel solution was spin-coated on this PZT film (3000 rpm, 30 seconds), and a Pt electrode was formed thereon as an upper electrode. Then, as shown in FIG. 16, a third heat treatment is performed at 150 ° C. for 120 minutes under a pressure of 9.9 atm and in a nitrogen atmosphere, and composite oxidation is performed at the interface between the PZT film and the upper Pt electrode. A PbPt ₃ film that is an alloy of Pb, which is a metal material of the product, and Pt, which is a metal material of the upper Pt electrode, is formed, and then a rapid thermal annealing method is used in a pressurized state in the same manner as in the second heat treatment. Post-annealing was performed to obtain a ferroelectric capacitor.

  In addition, as a comparative example with the ferroelectric capacitor obtained by the manufacturing method of this example, a ferroelectric capacitor using a conventional method (hereinafter, Conventional Method 2) was manufactured. In the conventional method 2, a raw material solution was used in which Pb was added to the sol-gel solution adjusted to a stoichiometric composition so that the molar ratio was 20% excess. And the process of carrying out the spin coating (3000 rpm, 30 second) of these on a Pt electrode, and pre-baking a raw material solution for 5 minutes at 400 degreeC was repeated 3 times, and the raw material body of 150 nm was formed. Next, as shown in FIG. 4, the temperature is raised to 650 ° C. at a rate of 100 ° C./second using a rapid thermal annealing method in an atmosphere containing atmospheric pressure and sufficient oxygen, and heat treatment is performed for 10 minutes. To obtain a PZT film on the Pt electrode. Next, an upper electrode was formed on the PZT film, and then post-annealing was performed using a rapid thermal annealing method in a pressurized state, whereby a ferroelectric capacitor according to the conventional method 2 was obtained.

In this way, after applying the 2V, 66 Hz triangular wave pulse 10 times to the obtained ferroelectric capacitor by the manufacturing method of the present example and the manufacturing method of the conventional method 2, the square wave pulse of 1.5V, 500 kHz was applied 10 times. Fatigue characteristics were investigated by applying polarization inversion ⁸ times or more.

  FIG. 17A to FIG. 17D are diagrams showing such fatigue characteristics. 17A and 17C show the case of the conventional method 2, and FIGS. 17B and 17D show the case of the manufacturing method of this example.

According to FIG. 17 (A), in the case of the conventional method 2, the characteristics are rapidly deteriorated in the vicinity where the number of polarization inversions exceeds 10 ⁸ , whereas according to FIG. 17 (B), In the case of this example, even if the number of polarization inversions exceeds 10 ⁸ , no characteristic deterioration due to fatigue is observed. Further, as shown in FIGS. 17 (C) and 17 (D), when the change in the hysteresis characteristics before and after the fatigue test is compared, according to FIG. 17 (C), the ferroelectric capacitor according to the conventional method 2 is fatigued. After the test, almost no hysteresis characteristics are shown, but according to FIG. 17D, the ferroelectric capacitor according to this example has a squareness equivalent to that before the test even after the fatigue test. Hysteresis shape is obtained. This is considered to be because in the ferroelectric capacitor of this example, an alloy film is formed at the upper and lower electrode interfaces of the PZT film, and distortion due to lattice mismatch is alleviated. Further, in the manufacturing method of this example, since crystallization heat treatment is performed by rapid heating using a rapid thermal annealing method in a pressurized and low oxygen state, Pb desorption is prevented during the crystallization process. It is considered that the highly oriented PZT film and the uniform PZT film also contribute to the improvement of fatigue characteristics.

  As described above, in the manufacturing method of the present embodiment, the ceramic film crystal is subjected to the alloy film formation process at the upper and lower interfaces of the ceramic film and the heat treatment using the rapid thermal annealing method in the pressurized and low oxygen state. It was confirmed that the ferroelectric capacitor has good hysteresis characteristics and fatigue characteristics.

[Third Embodiment]
In the present embodiment, application examples of the manufacturing method described in the first and second embodiments to a device will be described.

(Application example 1)
FIG. 18 is a cross-sectional view schematically showing a semiconductor device 100 to which the ceramic film obtained by the manufacturing method described in each of the above embodiments is applied.

  The semiconductor device 100 has a MISFET (metal-insulating film-semiconductor FET) structure in which a gate insulating film 140 and a gate electrode 150 are formed on a semiconductor substrate 110 provided with source and drain regions 120 and 130.

  In the semiconductor 100, the source and drain regions 120 and 130 can be formed using a known semiconductor manufacturing method. The gate electrode 150 can also be formed using a known semiconductor manufacturing method. The gate insulating film 140 is a ferroelectric ceramic film formed by using the ferroelectric capacitor manufacturing method described in the above embodiment. In order to form a good interface between the gate insulating film 140 and the semiconductor substrate 110, a paraelectric layer or a double layer made of metal and paraelectric may be inserted between the two.

  The semiconductor device 100 according to the present embodiment functions as a semiconductor memory by reading information using a change in drain current based on the polarization of the gate insulating film 140 that is a ferroelectric ceramic film. Since the gate insulating film 140 in the semiconductor device 100 is composed of a ferroelectric ceramic film obtained by using the manufacturing method described in the above embodiment, it has a hysteresis characteristic that saturates at a low voltage. Therefore, the semiconductor device 100 according to the present embodiment can be driven at a high speed or a low voltage, and the power consumption of the element can be reduced.

(Application example 2)
FIGS. 19A and 19B are views schematically showing a semiconductor device 1000 using a ferroelectric capacitor obtained by the manufacturing method of the above embodiment. Note that FIG. 19A shows a planar shape of the semiconductor device 1000, and FIG. 19B shows an AA ′ cross section in FIG. 19A.

  As illustrated in FIG. 19A, the semiconductor device 1000 includes a memory cell array 200 and a peripheral circuit portion 300. The memory cell array 200 and the peripheral circuit unit 300 are formed in different layers. The peripheral circuit unit 300 is arranged in a different region on the semiconductor substrate 400 with respect to the memory cell array 200. Specific examples of the peripheral circuit 300 include a Y gate, a sense amplifier, an input / output buffer, an X address decoder, a Y address decoder, or an address buffer.

  The memory cell array 200 is arranged so that a lower electrode 210 (word line) for row selection and an upper electrode 220 (bit line) for column selection intersect. The lower electrode 210 and the upper electrode 220 have a stripe shape composed of a plurality of line-shaped signal electrodes. The signal electrode can be formed so that the lower electrode 210 is a bit line and the upper electrode 220 is a word line.

  As shown in FIG. 19B, a ferroelectric ceramic film 215 is disposed between the lower electrode 210 and the upper electrode 220. In the memory cell array 200, a memory cell that functions as the ferroelectric capacitor 230 is formed in a region where the lower electrode 210 and the upper electrode 220 intersect. The ferroelectric capacitor 230 is formed using the manufacturing method according to the above embodiment. Therefore, an alloy film made of a compound of the material of the ferroelectric ceramic film 215 and the material of the lower electrode 210 or the upper electrode 220 is formed at each interface between the ferroelectric ceramic film 215 and the lower electrode 210 and the upper electrode 220. Has been. Note that the ferroelectric ceramic film 215 may be disposed at least between the regions where the lower electrode 210 and the upper electrode 220 intersect.

  Furthermore, in the semiconductor device 1000, a second interlayer insulating film 430 is formed so as to cover the lower electrode 210, the ferroelectric layer 215, and the upper electrode 220. Further, an insulating protective layer 440 is formed on the second interlayer insulating film 430 so as to cover the wiring layers 450 and 460.

  As shown in FIG. 19A, the peripheral circuit unit 200 includes various circuits for selectively writing information to or reading information from the memory cell 200. For example, the peripheral circuit unit 200 selectively controls the lower electrode 210. A first driving circuit 310 for controlling the upper electrode 220, a second driving circuit 320 for selectively controlling the upper electrode 220, and a signal detection circuit (not shown) such as a sense amplifier. .

  In addition, the peripheral circuit portion 300 includes a MOS transistor 330 formed on the semiconductor substrate 400 as shown in FIG. The MOS transistor 330 includes a gate insulating film 332, a gate electrode 334, and source / drain regions 336. The MOS transistors 330 are separated from each other by an element isolation region 410. On the semiconductor substrate 400 on which the MOS transistor 330 is formed, a first interlayer insulating film 410 is formed. The peripheral circuit unit 300 and the memory cell array 200 are electrically connected by the wiring layer 51.

  Next, an example of writing and reading operations in the semiconductor device 1000 will be described.

  First, in the read operation, a read voltage is applied to the capacitor of the selected memory cell. This also serves as a write operation of “0” at the same time. At this time, the current flowing through the selected bit line or the potential when the bit line is set to high impedance is read by the sense amplifier. A predetermined voltage is applied to the capacitors of unselected memory cells in order to prevent crosstalk during reading.

  In the write operation, in the case of “1” write, a write voltage for inverting the polarization state is applied to the capacitor of the selected memory cell. In the case of writing “0”, a write voltage that does not reverse the polarization state is applied to the capacitor of the selected memory cell, and the “0” state written during the read operation is held. At this time, a predetermined voltage is applied to the capacitor of the unselected memory cell in order to prevent crosstalk during writing.

  In this semiconductor device 1000, the ferroelectric capacitor 230 manufactured by the manufacturing method of the above embodiment has a hysteresis characteristic that saturates at a low voltage. Therefore, according to this semiconductor device 1000, it can be driven at a low voltage or high speed, and the power consumption of the element can be reduced. In addition, since the ferroelectric capacitor 230 has good fatigue characteristics, according to the semiconductor device 1000, the reliability of the element is high and the yield can be improved.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and can take various forms within the scope of the gist of the present invention.

It is a figure which shows the manufacturing process of 1st Embodiment. It is a figure which shows the heat processing in the manufacturing process of Example 1 of 1st Embodiment. It is a microscope picture of the ceramic film which concerns on Example 1 of 1st Embodiment. FIG. 3 is a view showing heat treatment in a manufacturing process of a conventional method in Example 1. It is a figure which shows the Raman scattering spectrum of the ceramic film which concerns on Example 1 of 1st Embodiment. It is a figure which shows the hysteresis characteristic of the ferroelectric capacitor which concerns on Example 1 of 1st Embodiment. It is a figure which shows the hysteresis characteristic of the ferroelectric capacitor which concerns on Example 1 of 1st Embodiment. It is a microscope picture of the ceramic film which concerns on Example 2 of 1st Embodiment. It is a microscope picture of the ceramic film which concerns on Example 2 of 1st Embodiment. It is a figure which shows the hysteresis characteristic of the ferroelectric capacitor which concerns on Example 2 of 1st Embodiment. It is a figure which shows the temperature characteristic of the ferroelectric capacitor which concerns on Example 2 of 1st Embodiment. It is a figure which shows the temperature characteristic of the ferroelectric capacitor which concerns on Example 2 of 1st Embodiment. It is a figure which shows the hysteresis characteristic of the ferroelectric capacitor which concerns on Example 3 of 1st Embodiment. It is a figure which shows the hysteresis characteristic of the ferroelectric capacitor which concerns on Example 4 of 1st Embodiment. It is a figure which shows the manufacturing process of 2nd Embodiment. It is a figure which shows the heat processing in the manufacturing process of the Example of 2nd Embodiment. It is a figure which shows the fatigue characteristic of the ferroelectric capacitor which concerns on the Example of 2nd Embodiment. It is a figure which shows the semiconductor device which concerns on the application example 1 of 3rd Embodiment. It is a figure which shows the semiconductor device which concerns on the application example 2 of 3rd Embodiment.

Explanation of symbols

10 substrate, 20 lower electrode, 24 lower alloy film, 30 raw material body, 40 ceramic film, 50 upper electrode

Claims (5)

Forming at least a lower electrode, a ceramic film, and an upper electrode on the substrate;
A method of manufacturing a ferroelectric capacitor, comprising performing a heat treatment for recovering ferroelectric characteristics in a state of being pressurized to 2 atm or more after forming at least the upper electrode. Forming at least a lower electrode, a ceramic film, and an upper electrode on the substrate;
A method for manufacturing a ferroelectric capacitor, comprising: performing a heat treatment for restoring ferroelectric characteristics in a state where the ceramic film is etched to a given shape at least and then pressurized to 2 atm or higher. In claim 1 or 2,
The method for manufacturing a ferroelectric capacitor, wherein the heat treatment for recovering the ferroelectric characteristics is performed using a rapid thermal annealing method.   A ferroelectric capacitor formed by the manufacturing method according to claim 1.   A semiconductor device comprising the ferroelectric capacitor according to claim 4.

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