JP3583638B2 - Ferroelectric capacitor and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ferroelectric capacitor and a method for manufacturing the same.
[0002]
[Prior art]
Ferroelectric materials constituting the ferroelectric capacitor include lead zirconate titanate: Pb (Zr _1-x Ti _x ) O ₃ (Hereinafter referred to as “PZT”), Bi layered compound: SrBi ₂ Ta ₂ O ₉ (Hereinafter, referred to as “SBT”) are often used. For this reason, a metal or conductive oxide having excellent oxidation resistance has been used for an electrode in contact with a ferroelectric layer formed of a ferroelectric substance.
[0003]
Conventionally, in the case of a ferroelectric capacitor provided with a metal electrode formed of a metal having excellent oxidation resistance, for example, an upper electrode is formed of Pt, and a lower electrode is formed by stacking a Pt layer and a Ti layer (hereinafter, referred to as “Pt”). / Ti lamination "). Here, the Ti layer is formed by forming the underlying layer of the lower electrode from SiO 2. ₂ If it is a layer, a Pt layer and SiO ₂ It is used to improve the adhesion to the layer.
[0004]
On the other hand, IrO ₂ And RuO ₂ When a conductive oxide such as this is used for the upper and lower electrodes, the barrier effect against diffusion is improved as compared with the Pt electrode. In addition, since these conductive oxides do not show a catalytic action on hydrogen, the fatigue characteristics and hydrogen resistance of the ferroelectric capacitor are improved.
[0005]
[Problems to be solved by the invention]
However, in general, IrO ₂ And RuO ₂ Since conductive oxides such as have a lower crystal orientation than Pt, the crystallinity of the ferroelectric film formed on the conductive oxide is lower than that formed on the Pt layer. Will be inferior. As a result, the ferroelectric capacitor having the conductive oxide electrode was inferior in ferroelectric characteristics as compared with the ferroelectric capacitor having the Pt electrode. Further, the fact that the resistivity of the conductive oxide electrode is higher by about one order of magnitude than the resistivity of the Pt electrode has also been a problem in terms of electrical characteristics.
[0006]
The present invention has been made in view of the above-mentioned problems, and has as its object to provide a ferroelectric capacitor having excellent hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance, and a method of manufacturing the same. Is to provide.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, According to a first aspect of the present invention, A ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode is provided. The ferroelectric layer of the ferroelectric capacitor is made of lead zirconate titanate, and one electrode includes a Pt / Ti laminate in which a Pt layer and a Ti layer are laminated. In such a configuration, by performing a heat treatment after the Pt / Ti stack is formed, Ti from the Ti layer is thermally diffused to the surface of the Pt layer. Then, by stacking a ferroelectric layer on the Pt / Ti stack, surplus Pb in lead zirconate titanate constituting the ferroelectric layer reacts with Ti on the surface of the Pt layer, and lead titanate is removed. Will be formed. This lead titanate is oriented in the <111> axis, and as a result, lead zirconate titanate constituting the ferroelectric layer can also be strongly oriented in the <111> axis. Further, since the lattice constant of the Pt layer increases due to thermal diffusion of Ti from the Ti layer, the lattice matching between the (111) plane of the Pt layer and the (111) plane of the ferroelectric layer made of lead zirconate titanate is performed. Is good.
[0008]
Also, In order to solve the above problems, according to a second aspect of the present invention, A ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode is provided. The ferroelectric layer is made of lead zirconate titanate, and at least one of the one electrode and the other electrode includes a lead titanate layer in contact with the ferroelectric layer. Lead titanate is oriented in the <111> axis, and the lead titanate layer made of lead titanate is in contact with the ferroelectric layer. It is possible to orient strongly to the 111> axis. In particular, by providing a lead titanate layer on both one electrode and the other electrode, it becomes possible to more uniformly crystallize lead zirconate titanate constituting the ferroelectric layer.
[0009]
One electrode includes a Pt layer, and the lead titanate layer included in one electrode is in contact with the ferroelectric layer on one surface and is in contact with the Pt layer on the other surface. Is preferred . Since Pt has strong self-orientation, it is possible to improve the <111> -axis crystal orientation of lead titanate constituting the lead titanate layer. Furthermore, it is possible to increase the degree of <111> axis preferential orientation of lead zirconate titanate constituting the ferroelectric layer in contact with the lead titanate layer.
[0010]
It is preferable that at least one of the one electrode and the other electrode includes an Au layer or an Ag layer. Au and Ag have excellent oxidation resistance and do not have a catalytic effect on hydrogen, so that the composition of lead zirconate titanate constituting the ferroelectric layer can be stabilized. Since Au and Ag have good crystal matching with the (111) plane of lead zirconate titanate constituting the ferroelectric layer, for example, the Au layer or the Ag layer may be in contact with the ferroelectric layer. If formed, the lead zirconate titanate constituting the ferroelectric layer can be more uniformly crystallized.
[0011]
Also , One electrode and at least one of the other electrodes preferably include an iridium oxide layer. According to this configuration, the diffusion of the constituent atoms of the lead zirconate titanate constituting the ferroelectric layer during the heat treatment and the application of the electric field is prevented, and the reduction resistance is also improved.
[0012]
To solve the above problems, according to a third aspect of the present invention, A method for manufacturing a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode is provided. This manufacturing method includes a step of forming a Ti layer forming one electrode, a step of stacking a Pt layer forming one electrode on the Ti layer, a step of performing a heat treatment, and a step of performing zirconium titanate. The method is characterized by including a step of forming a ferroelectric layer made of lead oxide and a step of forming another electrode. According to this manufacturing method, a heat treatment is performed when the Pt layer and the Ti layer are laminated, and the heat from the Ti layer is thermally diffused to the surface of the Pt layer by the heat treatment. In a subsequent step, a ferroelectric layer is further laminated on the Pt / Ti lamination, and excess Pb in lead zirconate titanate constituting the ferroelectric layer reacts with Ti on the surface of the Pt layer to form titanic acid. Lead will be formed. The lead titanate is oriented in the <111> axis, and as a result, it becomes possible to strongly orient the lead zirconate titanate constituting the ferroelectric layer in the <111> axis. Further, since the lattice constant of the Pt layer increases due to thermal diffusion of Ti from the Ti layer, the lattice matching between the (111) plane of the Pt layer and the (111) plane of the ferroelectric layer made of lead zirconate titanate is performed. Is good.
[0013]
In order to solve the above problems, according to a fourth aspect of the present invention, A method for manufacturing a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode is provided. The manufacturing method includes a step of forming one electrode, a step of forming a ferroelectric layer, a step of forming a protective layer constituting another electrode, and a step of performing instantaneous thermal annealing. It is characterized by. According to this manufacturing method, the ferroelectric layer is annealed after the protection layer is formed. An Au layer or an Ag layer can be used as the protective layer. Au and Ag have excellent oxidation resistance and do not have a catalytic effect on hydrogen, so that a change in the composition of the ferroelectric layer due to annealing is prevented. Further, since instantaneous thermal annealing is used, it is possible to minimize the composition deviation of the constituent atoms of the ferroelectric layer due to thermal diffusion. For example, when the ferroelectric layer is composed of lead zirconate titanate, Au and Ag have good crystal matching with the (111) plane of such lead zirconate titanate. Lead acid can be uniformly crystallized.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a ferroelectric capacitor and a method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, components having substantially the same functions and configurations are denoted by the same reference numerals, and redundant description is omitted.
[0015]
(First Embodiment)
A configuration of a ferroelectric capacitor 1 according to a first embodiment of the present invention and a method of manufacturing the same will be described with reference to FIG.
[0016]
First, the SiO substrate is ₂ A layer 200 (about 200 nm) is formed.
[0017]
Next, IrO ₂ A lower electrode composed of the layer 10, the Ti layer 20, and the Pt layer 30 is formed. SiO ₂ IrO on layer 200 ₂ The layer 10 (about 150 to 200 nm) is formed by a reactive sputtering method. A Ti layer 20 (about 10 to 20 nm) is formed thereon by a sputtering method, and a Pt layer 30 (about 200 nm) is further formed thereon by a sputtering method.
[0018]
Here, heat treatment is performed in an electric furnace at about 350 ° C. for about 15 minutes. The purpose of this heat treatment is to thermally diffuse Ti from the Ti layer 20 to the Pt layer 30 and to increase the lattice constant of Pt.
[0019]
After the heat treatment, a PZT layer 35 made of PZT, which is a ferroelectric substance, is formed on the Pt layer 30, and crystallization annealing is performed.
[0020]
Finally, IrO as upper electrode ₂ The layer 40 is formed.
[0021]
The main reason for using the Pt layer 30 made of Pt as the uppermost layer of the lower electrode in the ferroelectric capacitor 1 according to the first embodiment configured as described above is that the PZT layer 35 is formed of <111>. This is for the purpose of preferential orientation to the axis. Since Pt has strong self-orientation to the <111> axis, it is considered that a PZT crystal having good lattice matching with the Pt (111) plane is likely to grow. Since the PZT (111) plane corresponds to the Pt (111) plane, the PZT layer 35 formed on the Pt layer 30 is preferentially oriented along the <111> axis.
[0022]
Unlike the lower electrode composed of the Pt layer 30 and the Ti layer 20 as described above, ₂ When the Pt layer 30 is directly laminated on the layer 200 and the lower electrode composed of only the Pt layer 30 is formed, as apparent from the result of the X-ray diffraction shown in FIG. The preferred orientation weakens. In FIG. 2, the solid line indicates the X-ray diffraction pattern of the PZT layer formed on the Pt / Ti stack, and the broken line indicates the X-ray diffraction pattern of the PZT layer formed on the Pt layer. I have.
[0023]
Further, a clear difference appears also in the hysteresis characteristic of FIG. 3 and the remanent polarization saturation characteristic of FIG. In FIGS. 3 and 4, plots with black circles show the characteristics of the PZT layer formed on the Pt / Ti stack, and plots with white triangles show the characteristics of the PZT layer formed on the Pt layer. Is shown. As described above, as the priority degree of orientation of the PZT layer 35 to the <111> axis increases, the ferroelectric characteristics such as the hysteresis characteristics and the remanent polarization saturation characteristics improve.
[0024]
Even if the surface in contact with the PZT layer 35 is the Pt layer 30, it is considered that the crystal growth mechanism of PZT is involved as a cause of the difference in ferroelectric characteristics depending on the presence or absence of the Ti layer 20. As described above, in the manufacturing process of the ferroelectric capacitor 1 according to the first embodiment, the heat treatment is performed when the Ti layer 20 and the Pt layer 30 are stacked. By this heat treatment, Ti constituting the Ti layer 20 is thermally diffused to the surface of the Pt layer 30, that is, the surface on which the PZT layer 35 is formed later. The Ti diffused into the surface of the Pt layer 30 reacts with excess Pb in the PZT layer 35, and leads to a relatively low crystallization temperature of lead titanate PbTiO. ₃ (Hereinafter, referred to as “PTO”). That is, the Ti layer 20 functions to indirectly generate PTO at the interface between the PZT layer 35 and the Pt layer 30. Then, it is considered that crystallization of the PZT layer 35 proceeds with the PTO oriented in the <111> axis as a nucleus.
[0025]
As described above, according to the ferroelectric capacitor 1 according to the first embodiment, the lower electrode including the Pt / Ti stack is subjected to the heat treatment, and the PTO is formed at the interface between the Pt layer 30 and the PZT layer 35. Is generated, and as a result, so-called heteroepitaxial growth from the PTO to the PZT layer 35 is realized.
[0026]
In addition, since the lattice constant of the Pt layer 30 increases due to the thermal diffusion of Ti from the Ti layer 20, the lattice matching between the (111) plane of the Pt layer 30 and the (111) plane of the PZT layer 35 is further improved.
[0027]
Further, the IrO provided in the ferroelectric capacitor 1 according to the first embodiment is ₂ Layer 10 and IrO ₂ The layer 40 prevents the constituent atoms of the PZT layer 35 from diffusing at the time of heat treatment and application of an electric field, and improves the reduction resistance.
[0028]
As described above, the ferroelectric capacitor 1 according to the first embodiment has improved hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance over the conventional ferroelectric capacitors. Become. Further, the resistivity of the electrode is the same as that of the conventional IrO. ₂ Significantly lower than single layer electrodes.
[0029]
(Second embodiment)
A ferroelectric capacitor 2 according to a second embodiment will be described with reference to FIG.
[0030]
The ferroelectric capacitor 2 according to the second embodiment differs from the ferroelectric capacitor 1 according to the first embodiment in that a PTO layer 33 is provided instead of the Pt layer 30 and the Ti layer 20. It has. That is, the ferroelectric capacitor 2 is formed by using SiO 2 ₂ Layer 200, IrO ₂ Layer 10, PTO layer 33, PZT layer 35, and IrO ₂ The layers 40 are sequentially laminated.
[0031]
In the ferroelectric capacitor 1 according to the first embodiment, the Ti of the Ti layer 20 is thermally diffused to the surface of the Pt layer 30 and the excess Ti and the excess Pb of the PZT layer 35 react with each other, so to speak, indirectly. In which a PTO crystal nucleus is generated. However, the diffusion of Ti in the Pt layer 30 is fast, and it is not easy to control it to have a predetermined nucleation density.
[0032]
On the other hand, the ferroelectric capacitor 2 according to the second embodiment has an IrO ₂ On the layer 10, a PTO layer 33 serving as a crystal nucleus of the PZT layer 35 is formed thin (about several tens of degrees). The PTO layer 33 facilitates control of the nucleation density, and as a result, a very dense and uniform PZT crystal can be formed.
[0033]
(Third embodiment)
A ferroelectric capacitor 3 according to a third embodiment will be described with reference to FIG.
[0034]
The ferroelectric capacitor 3 according to the third embodiment is different from the ferroelectric capacitor 2 according to the second embodiment in that the PTO layer 33 and the IrO ₂ It has a configuration in which a Pt layer 30 is added between itself and the layer 10. That is, this ferroelectric capacitor 3 is formed by using a SiO.sub. ₂ Layer 200, IrO ₂ Layer 10, Pt layer 30, PTO layer 33, PZT layer 35, and IrO ₂ The layers 40 are sequentially laminated.
[0035]
The ferroelectric capacitor 2 according to the second embodiment is composed of IrO ₂ The PTO layer 33 is formed directly on the layer 10. However, since the <111> -axis crystal orientation of the PTO layer 33 is low, the PZT layer 35 formed thereon cannot obtain a sufficient <111> -axis crystal orientation. In this regard, in the ferroelectric capacitor 3 according to the third embodiment, the Pt layer 30 having strong self-orientation is composed of the PTO layer 33 and the IrO ₂ Since it is formed between the layers 10, the <111> axis crystal orientation of the PTO layer 33 is improved, and the <111> axis preferential orientation of the PZT layer 35 is also increased. Therefore, according to the ferroelectric capacitor 3 according to the third embodiment, high hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance can be obtained.
[0036]
(Fourth embodiment)
A ferroelectric capacitor 4 according to a fourth embodiment will be described with reference to FIG.
[0037]
The ferroelectric capacitor 4 according to the fourth embodiment is different from the ferroelectric capacitor 1 according to the first embodiment in that an IrO ₂ The structure has an Au layer 38 added between the layer 40 and the PZT layer 35. That is, the ferroelectric capacitor 4 is formed by using a SiO.sub. ₂ Layer 200, IrO ₂ Layer 10, Ti layer 20, Pt layer 30, PZT layer 35, Au layer 38, and IrO ₂ The layers 40 are sequentially laminated. After the Au layer 38 is formed, the crystallization annealing of the PZT layer 35 is performed by an instantaneous thermal annealing (hereinafter, referred to as “RTA”) process (700 ° C., 1 minute) in an oxygen atmosphere.
[0038]
Conventionally, the crystallization annealing of the ferroelectric has been performed immediately after the formation of the ferroelectric film. For this reason, the ferroelectric crystallized under the influence of only the lower electrode, was likely to have large crystal grains, and to have crystals having different compositions in the depth direction. In this regard, the ferroelectric capacitor 4 according to the fourth embodiment has good crystal matching with the (111) plane of the PZT layer 35, excellent oxidation resistance, An Au layer 38 having no catalytic effect is used. After the formation of the Au layer 38, crystallization annealing is performed. Therefore, the ferroelectric constituting the PZT layer 35 is crystallized under the influence of both the upper and lower electrodes, and a dense ferroelectric film having small crystal grains is formed. Note that an Ag layer made of Ag may be used instead of the Au layer 38.
[0039]
Further, since RTA is used for crystallization annealing, the composition deviation of the ferroelectric film due to thermal diffusion of constituent atoms can be minimized. As shown in FIG. 8, when the furnace annealing was used (broken line in the figure), when RTA was used (solid line in the figure), the <111> axis orientation of the upper and lower electrodes was more strongly reflected. A PZT layer 35 preferentially oriented in the 111> axis is formed.
[0040]
(Fifth embodiment)
A ferroelectric capacitor 5 according to a fifth embodiment will be described with reference to FIG.
[0041]
The ferroelectric capacitor 5 according to the fifth embodiment is different from the ferroelectric capacitor 2 according to the second embodiment in that an IrO ₂ The structure has an Au layer 38 added between the layer 40 and the PZT layer 35. That is, the ferroelectric capacitor 5 is formed by using a SiO.sub. ₂ Layer 200, IrO ₂ Layer 10, PTO layer 33, PZT layer 35, Au layer 38, and IrO ₂ The layers 40 are sequentially laminated. After the Au layer 38 is formed, the crystallization annealing of the PZT layer 35 is performed by an RTA process (700 ° C., 1 minute) in an oxygen atmosphere.
[0042]
The ferroelectric capacitor 5 according to the fifth embodiment has good crystal matching with the (111) plane of the PZT layer 35, has excellent oxidation resistance, and has a catalytic effect on hydrogen as a component of the upper electrode. Au layer 38 having no is used. After the formation of the Au layer 38, crystallization annealing is performed. Therefore, the ferroelectric constituting the PZT layer 35 is crystallized while being affected by both the upper and lower electrodes, and the dense ferroelectric film having small crystal grains is formed similarly to the ferroelectric capacitor 4 according to the fourth embodiment. Is formed. Note that an Ag layer made of Ag may be used instead of the Au layer 38.
[0043]
Further, since RTA is used for crystallization annealing, the composition deviation of the ferroelectric film due to thermal diffusion of constituent atoms can be minimized. As shown in FIG. 8, when the furnace annealing was used (broken line in the figure), when RTA was used (solid line in the figure), the <111> axis orientation of the upper and lower electrodes was more strongly reflected. A PZT layer 35 preferentially oriented in the 111> axis is formed.
[0044]
Further, the ferroelectric capacitor 5 according to the fifth embodiment has an IrO ₂ On the layer 10, a PTO layer 33 serving as a crystal nucleus of the PZT layer 35 is formed thin (for example, several tens to 100 degrees). The PTO layer 33 facilitates control of the nucleation density, and as a result, a very dense and uniform PZT crystal can be formed.
[0045]
(Sixth embodiment)
A ferroelectric capacitor 6 according to a sixth embodiment will be described with reference to FIG.
[0046]
The ferroelectric capacitor 6 according to the sixth embodiment is different from the ferroelectric capacitor 3 according to the third embodiment in that an IrO ₂ The structure has an Au layer 38 added between the layer 40 and the PZT layer 35. That is, the ferroelectric capacitor 6 is formed by using a SiO.sub. ₂ Layer 200, IrO ₂ Layer 10, Pt layer 30, PTO layer 33, PZT layer 35, Au layer 38, and IrO ₂ The layers 40 are sequentially laminated. After the Au layer 38 is formed, the crystallization annealing of the PZT layer 35 is performed by an RTA process (700 ° C., 1 minute) in an oxygen atmosphere.
[0047]
The ferroelectric capacitor 6 according to the sixth embodiment has good crystal matching with the (111) plane of the PZT layer 35, has excellent oxidation resistance, and has a catalytic effect on hydrogen as a component of the upper electrode. Au layer 38 having no is used. After the formation of the Au layer 38, crystallization annealing is performed. Therefore, the ferroelectric constituting the PZT layer 35 is crystallized under the influence of both the upper and lower electrodes, and the dense ferroelectric capacitors 4 and 5 of the fourth and fifth embodiments have small crystal grains. A ferroelectric film will be formed. Note that an Ag layer made of Ag may be used instead of the Au layer 38.
[0048]
Further, since RTA is used for crystallization annealing, the composition deviation of the ferroelectric film due to thermal diffusion of constituent atoms can be minimized. As shown in FIG. 8, when the furnace annealing was used (broken line in the figure), when RTA was used (solid line in the figure), the <111> axis orientation of the upper and lower electrodes was more strongly reflected. A PZT layer 35 preferentially oriented in the 111> axis is formed.
[0049]
Further, in the ferroelectric capacitor 6 according to the sixth embodiment, the Pt layer 30 having strong self-orientation has the PTO layer 33 and the IrO ₂ Since it is formed between the layers 10, the <111> axis crystal orientation of the PTO layer 33 is improved, and the <111> axis preferential orientation of the PZT layer 35 is also increased. Therefore, according to the ferroelectric capacitor 6 according to the sixth embodiment, high hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance can be obtained.
[0050]
(Seventh embodiment)
A ferroelectric capacitor 7 according to a seventh embodiment will be described with reference to FIG.
[0051]
The ferroelectric capacitor 7 according to the seventh embodiment is different from the ferroelectric capacitor 2 according to the second embodiment in that an IrO ₂ It has a configuration in which a PTO layer 37 is added between the layer 40 and the PZT layer 35. That is, the ferroelectric capacitor 7 is formed by using the SiO.sub. ₂ Layer 200, IrO ₂ Layer 10, PTO layer 33, PZT layer 35, PTO layer 37, and IrO ₂ The layers 40 are sequentially laminated.
[0052]
The ferroelectric capacitor 2 according to the second embodiment has an IrO ₂ On the layer 10, a PTO layer 33 serving as a crystal nucleus of the PZT layer 35 is formed thin (for example, several tens to 100 degrees). The PTO layer 33 facilitates control of the nucleation density, and as a result, very dense and uniform PZT crystal grains can be formed.
[0053]
In addition, the ferroelectric capacitor 7 according to the seventh embodiment includes a PZT layer 35 and an IrO ₂ The PTO layer 37 is formed between the PTO layer 37 and the layer 40. Therefore, the PZT layer 35 is crystallized using not only the lower PTO layer 33 but also the upper PTO layer 37 as a nucleus. Therefore, according to the ferroelectric capacitor 7 according to the seventh embodiment, the PZT layer 35 composed of denser and more uniform PZT crystal grains is different from the ferroelectric capacitor 2 according to the second embodiment. Will be formed.
[0054]
(Eighth embodiment)
A ferroelectric capacitor 8 according to an eighth embodiment will be described with reference to FIG.
[0055]
The ferroelectric capacitor 8 according to the eighth embodiment is different from the ferroelectric capacitor 6 according to the sixth embodiment in that a PTO layer is provided between the Au layer 38 and the PZT layer 35 constituting the upper electrode. 37 has the added configuration. That is, the ferroelectric capacitor 8 is formed by using the SiO.sub. ₂ Layer 200, IrO ₂ Layer 10, Pt layer 30, PTO layer 33, PZT layer 35, PTO layer 37, Au layer 38, and IrO ₂ The layers 40 are sequentially laminated.
[0056]
As described above, in the ferroelectric capacitor 6 according to the sixth embodiment, the Pt layer 30 having strong self-orientation is composed of the PTO layer 33 and the IrO ₂ Since it is formed between the layers 10, the <111> axis crystal orientation of the PTO layer 33 is improved, and the <111> axis preferential orientation of the PZT layer 35 is also increased. Therefore, according to the ferroelectric capacitor 6 according to the sixth embodiment, high hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance can be obtained.
[0057]
In addition, in the ferroelectric capacitor 7 according to the eighth embodiment, the PTO layer 37 is formed between the PZT layer 35 and the Au layer 38 constituting the upper electrode. For this reason, the PZT layer 35 is crystallized not only with the lower PTO layer 33 but also with the upper PTO layer 37 as a nucleus, and the <111> axis preferential orientation is improved. Therefore, according to the ferroelectric capacitor 8 according to the eighth embodiment, the PZT layer 35 composed of denser and more uniform PZT crystal grains is different from the ferroelectric capacitor 6 according to the sixth embodiment. Will be formed. Note that an Ag layer made of Ag may be used instead of the Au layer 38.
[0058]
As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those changes naturally fall within the technical scope of the present invention. It is understood to belong.
[0059]
【The invention's effect】
As described above, according to the ferroelectric capacitor and the method of manufacturing the same according to the present invention, the electric characteristics such as hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance, and the environmental resistance are improved. Will do.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a ferroelectric capacitor according to a first embodiment.
FIG. 2 is a characteristic diagram showing an X-ray diffraction pattern of a PZT layer formed on a Pt layer and an X-ray diffraction pattern of a PZT layer formed on a Pt / Ti stack.
FIG. 3 is a characteristic diagram showing hysteresis characteristics of a PZT layer formed on a Pt layer and hysteresis characteristics of a PZT layer formed on a Pt / Ti stack.
FIG. 4 is a characteristic diagram showing remanent polarization saturation characteristics of a PZT layer formed on a Pt layer and remanent polarization saturation characteristics of a PZT layer formed on a Pt / Ti stack.
FIG. 5 is a cross-sectional view illustrating a configuration of a ferroelectric capacitor according to a second embodiment.
FIG. 6 is a sectional view showing a configuration of a ferroelectric capacitor according to a third embodiment.
FIG. 7 is a cross-sectional view illustrating a configuration of a ferroelectric capacitor according to a fourth embodiment.
FIG. 8 is a characteristic diagram showing an X-ray diffraction pattern of a PZT layer formed on a Pt layer after electric furnace annealing and an X-ray diffraction pattern after RTA annealing.
FIG. 9 is a sectional view showing a configuration of a ferroelectric capacitor according to a fifth embodiment.
FIG. 10 is a sectional view showing a configuration of a ferroelectric capacitor according to a sixth embodiment.
FIG. 11 is a sectional view showing a configuration of a ferroelectric capacitor according to a seventh embodiment.
FIG. 12 is a cross-sectional view illustrating a configuration of a ferroelectric capacitor according to an eighth embodiment.
[Explanation of symbols]
1 Ferroelectric capacitors
10 IrO ₂ layer
20 Ti layer
30 Pt layer
33 PTO layer
35 PZT layer
37 PTO layer
38 Au layer
40 IrO ₂ layer
100 Si substrate
200 SiO ₂ layer

Claims (9)

A lower electrode comprising a first dielectric oxide layer;
A ferroelectric layer formed of lead zirconate titanate formed on the lower electrode,
An upper electrode including a second conductive oxide layer formed on the ferroelectric layer;
A ferroelectric capacitor having
And a Ti layer and a Pt layer formed on the Ti layer between the first conductive oxide layer and the ferroelectric layer.
A lead titanate layer generated by a reaction between Ti diffused from the Ti layer to the surface of the Pt layer and a part of the ferroelectric layer is formed at an interface between the Pt layer and the ferroelectric layer. A ferroelectric capacitor characterized by being formed . The lead titanate layer comprises:
2. The ferroelectric capacitor according to claim 1, wherein one surface is in contact with the ferroelectric layer, and the other surface is in contact with the Pt layer . 3. The ferroelectric capacitor according to claim 1, further comprising an Au layer between the upper electrode and the lower electrode . 3. The ferroelectric capacitor according to claim 1, further comprising an Ag layer between the upper electrode and the lower electrode . 5. The ferroelectric substance according to claim 1, wherein at least one of said first conductive oxide layer and said second conductive oxide layer is an iridium oxide layer. Capacitors. A lower electrode having a first dielectric oxide layer, a ferroelectric layer made of lead zirconate titanate, and an upper electrode having a second conductive oxide layer; A method of manufacturing a ferroelectric capacitor comprising a Ti layer and a Pt layer formed on the Ti layer between a conductive oxide layer and the ferroelectric layer,
  Forming the lower electrode on a substrate;
  Forming the Ti layer and the Pt layer on the lower electrode;
  Diffusing Ti from the Ti layer to the surface of the Pt layer by heat treatment, and thereafter forming the ferroelectric layer on the Pt layer;
  Forming the upper electrode on the ferroelectric layer;
A method for manufacturing a ferroelectric capacitor, comprising: Forming a protective layer on the ferroelectric layer;
Performing instantaneous thermal annealing on the ferroelectric layer on which the protective layer is formed;
Forming the upper electrode layer on the protective layer;
7. The method for manufacturing a ferroelectric capacitor according to claim 6, comprising : 8. The method according to claim 7, wherein the protection layer is an Au layer . The method according to claim 7, wherein the protection layer is an Ag layer .

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