JP2000223662A - Ferroelectric body capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric capacitor with superior hysteresis, residual polarization saturation, fatigue, and anti-reduction characteristics, and its manufacturing method. SOLUTION: A ferroelectric body capacitor 1 is composed of an Si substrate 100, an SiO2 layer 200, an IrO2 layer 10, a Ti layer 20, a Pt layer 30, a PZT(lead zirconate titanate) layer 35, and an IrO2 layer 40. When the Pt layer 30 is formed, heat treatment is made at approximately 350 deg.C for approximately 15 minutes in an electric oven. Due to the heat treatment, Ti for composing the Ti layer 20 is thermally diffused to the surface of the Pt layer 30, namely, a surface where the PZT layer 35 is formed later. The Ti being diffused on the surface of the Pt layer 30 reacts to surplus Pd in the PZT layer 35 for forming lead titanate PbTiO3 with relatively low crystallization temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric capacitor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Ferroelectric materials constituting a ferroelectric capacitor include lead zirconate titanate: Pb (Zr
_{1-x Ti x) O 3} ( hereinafter referred to as "PZT".), B
i-layered compound: SrBi ₂ Ta ₂ O ₉ (hereinafter referred to as “SB
T ". ) And the like 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.

Conventionally, in the case of a ferroelectric capacitor provided with a metal electrode formed of a metal having excellent oxidation resistance, for example,
The upper electrode was formed by Pt, and the lower electrode was formed by stacking a Pt layer and a Ti layer (hereinafter, referred to as “Pt / Ti stack”). Here, the Ti layer is made of Pt when the underlying layer of the lower electrode is a SiO ₂ layer.
It is used to improve the adhesion between the layer and the SiO ₂ layer.

On the other hand, when a conductive oxide such as IrO ₂ or RuO ₂ is used for the upper and lower electrodes, a barrier effect against diffusion is improved as compared with the Pt electrode. Further, since these conductive oxides do not show a catalytic action on hydrogen, the fatigue characteristics and the hydrogen resistance of the ferroelectric capacitor are improved.

[0005]

However, in general, conductive oxides such as IrO ₂ and RuO ₂ have poor crystal orientation compared to Pt. The crystallinity of the film is inferior to that formed on the Pt layer. 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. In addition, the fact that the resistivity of the conductive oxide electrode is about one order of magnitude higher than the resistivity of the Pt electrode has also been problematic in terms of electrical characteristics.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a ferroelectric capacitor and a ferroelectric capacitor having excellent hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics, and reduction resistance. It is to provide a manufacturing method thereof.

[0007]

In order to solve the above problems, there is provided a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode. The ferroelectric layer in this ferroelectric capacitor is made of lead zirconate titanate, and one electrode is a Pt / Ti layer in which a Pt layer and a Ti layer are laminated. It is characterized by including lamination. In such a configuration, Pt /
By performing a heat treatment after the Ti stack is formed,
Ti from the Ti layer is thermally diffused on the surface of the Pt layer. Then, by stacking a ferroelectric layer on the Pt / Ti stack, excess Pb in lead zirconate titanate constituting the ferroelectric layer reacts with Ti on the surface of the Pt layer,
Lead titanate 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. Also, Ti from the Ti layer
Since the lattice constant of the Pt layer increases due to the thermal diffusion of
The lattice matching between the (111) plane of the Pt layer and the (111) plane of the ferroelectric layer composed of lead zirconate titanate is improved.

According to a second aspect of the present invention, there is provided a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode. 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 since the lead titanate layer made of lead titanate is in contact with the ferroelectric layer, the lead zirconate titanate constituting the ferroelectric layer is replaced with < 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.

According to a third aspect, the one electrode is
The lead titanate layer including the Pt layer and included in one electrode is in contact with the ferroelectric layer on one side and Pd on the other side.
It is characterized by being in contact with the t-layer. According to this configuration, since Pt has strong self-orientation, it is possible to improve the <111> -axis crystal orientation of lead titanate constituting the lead titanate layer. Further, <111> of lead zirconate titanate constituting the ferroelectric layer in contact with the lead titanate layer
It becomes possible to increase the degree of axis priority orientation.

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 are
Since it has excellent oxidation resistance and does not have a catalytic effect on hydrogen, it is possible to stabilize the composition of lead zirconate titanate constituting the ferroelectric layer. Au and Ag have good crystal matching with the (111) plane of lead zirconate titanate constituting the ferroelectric layer.
If the Au layer or the Ag layer is formed so as to be in contact with the ferroelectric layer, it is possible to more uniformly crystallize the lead zirconate titanate constituting the ferroelectric layer.

[0011] As described in claim 6, at least one of the one electrode and the other electrode preferably includes an iridium oxide layer. According to such a 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.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode. This manufacturing method includes a step of forming a Ti layer constituting one electrode, and a step of forming a Ti layer.
A step of laminating a Pt layer constituting one electrode, a step of performing a heat treatment, a step of forming a ferroelectric layer made of lead zirconate titanate, and a step of forming another electrode. And 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 laminate, and the excess Pb and Pt in the lead zirconate titanate constituting the ferroelectric layer are formed.
This reacts with Ti on the surface of the layer to form lead titanate. This lead titanate is oriented in the <111> axis, and as a result, it is possible to strongly orient the lead zirconate titanate constituting the ferroelectric layer in the <111> axis.
In addition, 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 good.

According to the present invention, there is provided a method of manufacturing a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode. 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 formation of the protective layer. As the protective layer, an Au layer or an Ag layer can be used. Au and Ag
Is excellent in oxidation resistance and has no catalytic effect on hydrogen, so that a change in the composition of the ferroelectric layer due to annealing can be 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]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Preferred embodiments of a ferroelectric capacitor and a method for manufacturing the same according to the present invention will be described in detail. 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.

(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.

First, an SiO ₂ layer 20 is formed on a Si substrate 100.
0 (about 200 nm).

Next, a lower electrode composed of the IrO ₂ layer 10, the Ti layer 20, and the Pt layer 30 is formed. IrO ₂ layer 10 (about 150 to 200 nm) on SiO ₂ layer 200
Is formed by a reactive sputtering method. A Ti layer 20 (about 10 to 20 nm) is formed thereon by sputtering, and a Pt layer 30 (about 200 nm) is further formed thereon by sputtering.

Here, a 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.

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.

Finally, an IrO ₂ layer 40 as an upper electrode is formed.

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 This is because the <111> axis is preferentially oriented. 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. The PZT (111) plane
Since it corresponds to the Pt (111) plane, the Pt layer 30
The PZT layer 35 formed thereon is preferentially oriented to the <111> axis.

The above Pt layer 30 and Ti layer 20
Unlike the lower electrode consisting of ₂Directly on layer 200
The Pt layer 30 is laminated, and the lower electrode composed only of the Pt layer 30 is formed.
When poles were formed, the results of X-ray diffraction shown in FIG.
As shown, the preferred orientation of the PZT layer 35 to the <111> axis
Weakens. In FIG. 2, the solid line represents the Pt / Ti product.
Shows the X-ray diffraction pattern of the PZT layer formed on the layer.
The broken line indicates the X-ray diffraction of the PZT layer formed on the Pt layer.
The folding pattern is shown.

Also, a clear difference appears in the hysteresis characteristic of FIG. 3 and the remanent polarization saturation characteristic of FIG. Note that FIG.
In FIG. 4, the plots with black circles show the characteristics of the PZT layer formed on the Pt / Ti stack, and the plots with white triangles show the characteristics of the PZT layer formed on the Pt layer. As described above, as the priority degree of orientation of the PZT layer 35 to the <111> axis is higher, ferroelectric characteristics such as hysteresis characteristics and remanent polarization saturation characteristics are improved.

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, T
The heat treatment is performed when the i-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 PbTi.
O ₃ (hereinafter, referred to as “PTO”) is formed. That is, the Ti layer 20 functions to indirectly generate PTO at the interface between the PZT layer 35 and the Pt layer 30. PZT with PTO oriented along the <111> axis as the core
It is considered that the crystallization of the layer 35 proceeds.

As described above, according to the ferroelectric capacitor 1 according to the first embodiment, the heat treatment is performed on the lower electrode including the Pt / Ti stack, and the Pt layer 30 and the PZT
PTO is generated at the interface with the layer 35, and as a result, so-called heteroepitaxial growth from the PTO to the PZT layer 35 is realized.

The thermal diffusion of Ti from the Ti layer 20 increases the lattice constant of the Pt layer 30.
The lattice matching between the (111) plane of the PZT layer 35 and the (111) plane of the PZT layer 35 is further improved.

Further, the ferroelectric according to the first embodiment
IrO provided in the body capacitor 1 ₂Layer 10 and Ir
O₂The layer 40 is made of PZ during heat treatment and electric field application.
Prevents diffusion of constituent atoms of T layer 35 and reduces resistance
Improve.

As described above, according to the first embodiment,
The ferroelectric capacitor 1 is different from a conventional ferroelectric capacitor.
On the other hand, hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics
And reduction resistance are improved. In addition,
The resistivity of the pole is the conventional IrO ₂Significantly lower than single-layer electrodes
Down.

(Second Embodiment) A ferroelectric capacitor 2 according to a second embodiment will be described with reference to FIG.

The ferroelectric capacitor 2 according to the second embodiment differs from the ferroelectric capacitor 1 according to the first embodiment in that instead of the Pt layer 30 and the Ti layer 20,
It has a configuration provided with a PTO layer 33. In other words, the ferroelectric capacitor 2 is formed such that the SiO ₂ layer 200, the IrO ₂ layer 10, the PTO layer 3
3, a PZT layer 35 and an IrO ₂ layer 40 are sequentially laminated.

In the ferroelectric capacitor 1 according to the first embodiment, the Ti of the Ti layer 20 is thermally diffused on the surface of the Pt layer 30, and the Ti reacts with the excess Pb of the PZT layer 35. It is characterized in that PTO crystal nuclei are generated indirectly. However, T in the Pt layer 30
The diffusion of i is fast and it is not easy to control it to a predetermined nucleation density.

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.
Is formed thinly (about several tens of kilometers). This PTO layer 3
3, the control of the nucleation density is facilitated, and as a result, a very dense and uniform PZT crystal can be formed.

(Third Embodiment) A ferroelectric capacitor 3 according to a third embodiment will be described with reference to FIG.

The ferroelectric capacitor 3 according to the third embodiment is different from the ferroelectric capacitor 2 according to the second embodiment in that a Pt layer is provided between the PTO layer 33 and the IrO ₂ layer 10. 30 has the added configuration.
That is, the ferroelectric capacitor 3 is
0, SiO 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.

In the ferroelectric capacitor 2 according to the second embodiment, the PTO layer 33 is formed directly on the IrO ₂ layer 10. However, since the <111> axis crystal orientation of the PTO layer 33 is low, the PZT layer 35
However, sufficient <111> axis crystal orientation cannot be obtained. In this regard, the ferroelectric capacitor 3 according to the third embodiment
Means that the Pt layer 30 having strong self-orientation is
Since the PTO layer 33 is formed between the rO ₂ layers 10,
<111> -axis crystal orientation is improved, and PZ
The <111> axis preferential orientation of the T layer 35 also increases.
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.

(Fourth Embodiment) A ferroelectric capacitor 4 according to a fourth embodiment will be described with reference to FIG.

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 layer 40 forming an upper electrode and a P
It has a configuration in which an Au layer 38 is added to the ZT layer 35. That is, this ferroelectric capacitor 4
Shows that the SiO ₂ layer 200, Ir
O ₂ layer 10, Ti layer 20, Pt layer 30, PZT layer 35,
An Au layer 38 and an IrO ₂ layer 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.

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, which constitutes the upper electrode, has good crystal matching with the (111) plane of the PZT layer 35, has excellent oxidation resistance, and has excellent hydrogen resistance. Layer 38 which has no catalytic effect on
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 a dense ferroelectric film having small crystal grains is formed. Note that instead of the Au layer 38, A
An Ag layer made of g may be used.

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 RTA was used (solid line in the figure), when the electric furnace annealing was used (broken line in the figure),
The <111> axis orientation is more strongly reflected, and a PZT layer 35 preferentially oriented in the <111> axis is formed.

(Fifth Embodiment) A ferroelectric capacitor 5 according to a fifth embodiment will be described with reference to FIG.

The ferroelectric capacitor 5 according to the fifth embodiment is different from the ferroelectric capacitor 2 according to the _second embodiment in that the IrO ₂ layer 40 forming the upper electrode and the P
It has a configuration in which an Au layer 38 is added to the ZT layer 35. That is, this ferroelectric capacitor 5
Shows that the SiO ₂ layer 200, Ir
O ₂ layer 10, PTO layer 33, PZT layer 35, Au layer 3
8, and an IrO ₂ layer 40 are sequentially laminated. Then, the crystallization annealing of the PZT layer 35 is performed using Au.
After the layer 38 is formed, RTA is performed in an oxygen atmosphere.
It is performed by processing (700 ° C., 1 minute).

The ferroelectric capacitor 5 according to the fifth embodiment has a PZT layer 3 as an upper electrode.
The Au layer 38 has good crystal matching with the (111) plane of No. 5, has excellent oxidation resistance, and has no catalytic effect on hydrogen. 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 instead of the Au layer 38, A
An Ag layer made of g may be used.

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 RTA was used (solid line in the figure), when the electric furnace annealing was used (broken line in the figure),
The <111> axis orientation is more strongly reflected, and a PZT layer 35 preferentially oriented in the <111> axis is formed.

Further, the ferroelectric capacitor 5 according to the fifth embodiment has an IrO ₂ layer 10 constituting a lower electrode.
On top, a PTO layer 33 serving as a crystal nucleus of the PZT layer 35 is formed thin (for example, several tens of degrees to 100 degrees). This P
The TO layer 33 facilitates control of the nucleation density,
As a result, a very dense and uniform PZT crystal can be formed.

(Sixth Embodiment) A ferroelectric capacitor 6 according to a sixth embodiment will be described with reference to FIG.

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 layer 40 forming an upper electrode and a P
It has a configuration in which an Au layer 38 is added to the ZT layer 35. That is, this ferroelectric capacitor 6
Shows that the SiO ₂ layer 200, Ir
O ₂ layer 10, Pt layer 30, PTO layer 33, PZT layer 3
5, an Au layer 38 and an IrO ₂ layer 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.

The ferroelectric capacitor 6 according to the sixth embodiment has a PZT layer 3 as an upper electrode.
The Au layer 38 has good crystal matching with the (111) plane of No. 5, has excellent oxidation resistance, and has no catalytic effect on hydrogen. After the formation of the Au layer 38, crystallization annealing is performed. Therefore, the ferroelectric material 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 according to the fourth and fifth embodiments have small crystal grains. A ferroelectric film will be formed. Note that, instead of the Au layer 38, an Ag layer made of Ag may be used.

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 RTA was used (solid line in the figure), when the electric furnace annealing was used (broken line in the figure),
The <111> axis orientation is more strongly reflected, and a PZT layer 35 preferentially oriented in the <111> axis is formed.

Further, in the ferroelectric capacitor 6 according to the sixth embodiment, the Pt layer 30 having strong self-orientation
Since it is formed between the TO layer 33 and the IrO ₂ layer 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 accordingly increased. Become. 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.

(Seventh Embodiment) A ferroelectric capacitor 7 according to a seventh embodiment will be described with reference to FIG.

The ferroelectric capacitor 7 according to the seventh embodiment is different from the ferroelectric capacitor 2 according to the _second embodiment in that the IrO ₂ layer 40 forming the upper electrode and the P
It has a configuration in which a PTO layer 37 is added to the ZT layer 35. That is, this ferroelectric capacitor 7
Shows that the SiO ₂ layer 200, Ir
O ₂ layer 10, PTO layer 33, PZT layer 35, PTO layer 3
7, and the IrO ₂ layer 40 are sequentially laminated.

The ferroelectric capacitor 2 according to the _second embodiment has a structure in which a P
The PTO layer 33 serving as a crystal nucleus of the ZT 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.

In addition, in the ferroelectric capacitor 7 according to the seventh embodiment, the PTO layer 37 is formed between the PZT layer 35 and the IrO ₂ layer 40 constituting the upper electrode. For this reason, 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 made of denser and more uniform PZT crystal grains is different from the ferroelectric capacitor 2 according to the second embodiment. Will be formed.

(Eighth Embodiment) A ferroelectric capacitor 8 according to an eighth embodiment will be described with reference to FIG.

The ferroelectric capacitor according to the eighth embodiment
The ferrule 8 is a ferroelectric capacitor according to the sixth embodiment.
The Au layer 38 forming the upper electrode and the PZT
It has a configuration in which a PTO layer 37 is added between itself and the layer 35.
Things. That is, this ferroelectric capacitor 8
For the Si substrate 100, SiO₂Layer 200, IrO ₂
Layer 10, Pt layer 30, PTO layer 33, PZT layer 35, P
TO layer 37, Au layer 38, and IrO₂Layer 40 is sequential
It is formed by lamination.

As described above, the ferroelectric capacitor 6 according to the sixth embodiment has a Pt layer 30 having strong self-orientation.
Is formed between the PTO layer 33 and the IrO ₂ layer 10, so that 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. Will be. 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.

In addition, in the ferroelectric capacitor 7 according to the eighth embodiment, a 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
In addition, crystallization is performed using the upper PTO layer 37 as a nucleus, and the <111> axis preferential orientation is improved. Therefore, the ferroelectric capacitor 8 according to the eighth embodiment
According to this, the PZT layer 35 made of denser and more uniform PZT crystal grains is formed on the ferroelectric capacitor 6 according to the sixth embodiment. The Au layer 3
Instead of 8, an Ag layer made of Ag may be used.

Although the preferred embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear 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 modifications naturally fall within the technical scope of the present invention. It is understood to belong.

[0059]

As described above, according to the ferroelectric capacitor and the method of manufacturing the same according to the present invention, electrical characteristics such as hysteresis characteristics, remanent polarization saturation characteristics, fatigue characteristics and reduction resistance, and Environment resistance is improved.

[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 an X-ray diffraction pattern of a PZT layer formed on a Pt layer, and PZ formed on a Pt / Ti stack.
FIG. 4 is a characteristic diagram showing an X-ray diffraction pattern of a T layer.

FIG. 3 shows a hysteresis characteristic of a PZT layer formed on a Pt layer and a PZT layer formed on a Pt / Ti stack.
FIG. 4 is a characteristic diagram showing a hysteresis characteristic of a T layer.

FIG. 4 shows remanent polarization saturation characteristics of a PZT layer formed on a Pt layer, and PZ formed on a Pt / Ti stack.
FIG. 4 is a characteristic diagram illustrating remanent polarization saturation characteristics of a T layer.

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 annealing in an electric furnace and an X-ray diffraction pattern after RTA annealing.

FIG. 9 is a cross-sectional view illustrating 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 sectional view showing a configuration of a ferroelectric capacitor according to an eighth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ferroelectric capacitor 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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 21/8247 29/788 29/792

Claims (10)

[Claims] 1. A ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode, wherein the ferroelectric layer is made of lead zirconate titanate, and the one electrode is A ferroelectric capacitor, comprising a Pt / Ti stack in which a Pt layer and a Ti layer are stacked. 2. A ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode, wherein the ferroelectric layer is made of lead zirconate titanate; And at least one of the other electrodes includes a lead titanate layer in contact with the ferroelectric layer. 3. The one electrode includes a Pt layer, and the lead titanate layer included in the one electrode is in contact with the ferroelectric layer on one surface and on the Pt layer on another surface.
3. The ferroelectric capacitor according to claim 2, wherein the capacitor is in contact with the layer. 4. The ferroelectric capacitor according to claim 1, wherein at least one of said one electrode and said another electrode includes an Au layer. 5. The ferroelectric capacitor according to claim 1, wherein at least one of the one electrode and the other electrode includes an Ag layer. 6. The ferroelectric device according to claim 1, wherein at least one of the one electrode and the other electrode includes an iridium oxide layer. Body capacitor. 7. A method for manufacturing a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode, the method comprising: forming a Ti layer constituting the one electrode;
Stacking a Pt layer constituting the one electrode on the layer, performing a heat treatment, forming the ferroelectric layer made of lead zirconate titanate, and forming the other electrode A method of manufacturing a ferroelectric capacitor. 8. A method for manufacturing a ferroelectric capacitor having a ferroelectric layer, one electrode, and another electrode, wherein the step of forming the one electrode and the step of forming the ferroelectric layer And a step of forming a protective layer constituting the another electrode, and a step of performing instantaneous thermal annealing. 9. The method according to claim 8, wherein the protection layer is an Au layer. 10. The method according to claim 8, wherein the protection layer is an Ag layer.