JP2000082782A - Ferroelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the electrical characteristics of a ferroelectric device. SOLUTION: In a ferroelectric device, for example, a phosphorus glass layer is formed on the surface of a ferroelectric film or removed after formation thereof (1), silicon nitride films 204 and 206 are formed on the surface of a ferroelectric film 205 (2), an electrode made of a titanium nitride film is formed at least at one place on the surface of the ferroelectric film (3), and two electrodes are formed oppositely at least on one main surface of the ferroelectric film, thus preventing the lack of oxygen caused by capturing an alkali metal movable ion in the ferroelectric and also by preventing discharge of oxygen, preventing segregation of composition elements, preventing deterioration in characteristics by making equal the interface level density between the electrode and the ferroelectric, and hence providing the ferroelectric device with secured electric characteristics, a long life, and stable characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a ferroelectric device.

[0002]

2. Description of the Related Art Conventionally, a ferroelectric device has been formed as follows. That is, a metal electrode opposed to two main surfaces of a ferroelectric film is usually formed.

[0003]

However, according to the above-mentioned prior art, alkalis such as sodium in the ferroelectric film are not used.
Due to the movement of ions such as ions due to the electric field, the segregation of the ferroelectric constituent elements such as oxygen and titanium due to the movement of the constituent elements due to the electric field, and the difference in the interface state between the electrode and the ferroelectric substance, etc. There have been problems in the stability of characteristics, such as a problem that the electrical characteristics of the dielectric are not constant and a problem that the life is short.

An object of the present invention is to provide a new ferroelectric device structure which solves the above-mentioned problems of the prior art.

[0005]

In order to solve the above problems and achieve the above object, the present invention relates to a ferroelectric device, which relates to (1) forming a phosphorus glass layer on the surface of a ferroelectric film;
Or (2) forming a silicon nitride film on the surface of the ferroelectric film; (3) forming an electrode comprising at least one titanium nitride film on the surface of the ferroelectric film. And (4) forming two electrodes facing each other at least on one main surface of the ferroelectric film.

[0006]

The phosphorus glass layer has a function of capturing alkali metal mobile ions in an oxide ferroelectric substance or a high dielectric constant substance, preventing deterioration of characteristics and stabilizing characteristics.

The silicon nitride film has an effect of preventing the release of oxygen from the oxide ferroelectric or the high dielectric constant, and of preventing deterioration of characteristics due to oxygen deficiency.

The titanium nitride electrode is formed by applying an electric field or a space charge limiting current to constituent elements of an oxide ferroelectric or high dielectric substance such as titanium or oxygen below the electrode provided on the oxide ferroelectric substance or high dielectric substance. Has the effect of preventing segregation due to carbon dioxide and stabilizing characteristics.

By providing a counter electrode on one principal surface of the oxide ferroelectric film or the high dielectric constant film, the interface state density between the electrode and the oxide ferroelectric film or the high dielectric constant film can be reduced. They can be made the same, and have an effect of preventing a change in characteristics due to reversal of polarity.

[0010]

The present invention will be described below in detail with reference to examples.

FIG. 1 is a sectional view of a main part of a ferroelectric device according to an embodiment of the present invention. That is, an insulating film 102 made of a silicon oxide film or a silicon nitride film is formed on a surface of a substrate 101 made of a semiconductor such as silicon, and an electrode 103 made of titanium-platinum or platinum is formed on the insulating film 102. Is formed to a thickness of about 10 nm, and lead / zirconium / titanium oxide (PZ) is formed on the electrode 103.
T), a ferroelectric film 105 such as lead / lanthanum / zirconium / titanium oxide (PLZT) or barium titanate, or a high dielectric constant oxide film such as tantalum oxide or titanium oxide having a thickness of 10 nm by sputtering deposition or the like.
When forming to a thickness of about 300 nm,
Phosphor glass in which phosphorus oxide is mixed with silicon oxide formed by the method D, or the ferroelectric film 105 or the high-dielectric-constant oxide film is formed, and phosphorus ions are implanted into the ferroelectric film 10.
5 or 4 mol of high dielectric constant oxide film by vitrifying phosphorus
% Of a phosphorus glass layer 103 having a phosphorus concentration of about 10% and a thickness of about 10 nm, and after forming the ferroelectric film 105 or the high-dielectric-constant oxide film, the phosphorus glass layer 106 is formed by the same method as described above. An electrode 107 made of titanium-platinum, platinum or the like is formed on the surface of the dielectric film 105 or the high-dielectric-constant oxide film to a thickness of about 10 nm. The phosphor glass layer 106 may be removed once it has been formed and then trapped by mobile ions.
3 or 106 may be formed so as to extend to the side surface of the ferroelectric film 105. The phosphor glass layer or the like may be not only a phosphor glass single layer but also a multilayer structure of titanium oxide, silicon oxide, or the like. Good. As described above, when a phosphorus glass layer is formed on a surface of a ferroelectric film or a high-k oxide film, the phosphorus glass layer captures mobile ions in the ferroelectric film or the high-k oxide film, This has the effect of preventing the characteristic deterioration of the ferroelectric film or the high-dielectric-constant oxide film due to mobile ions and stabilizing the characteristics. FIG. 2 is a sectional view of a main part of a ferroelectric device according to another embodiment of the present invention. That is, the substrate 2
After the electrode 203 is formed on the insulating film 202 formed on the silicon nitride film 01, the silicon nitride film 204 is
A ferroelectric film 205 or a high dielectric constant oxide film is formed to a thickness of about 10 nm to 300 nm, and then a silicon nitride film 206 is formed by a CVD method or the like.
Is formed to a thickness of about 10 nm to 50 nm, and then the electrode 20 is formed.
7, the silicon nitride film 203 or 206 may be formed to extend to the side surface of the ferroelectric film 205, or the silicon nitride film 203 or 206 may be formed of the ferroelectric film of the electrode 203 or 206. Body membrane 20
5 or the surface excluding the interface with the high-dielectric-constant oxide film, or in this case, may be formed to extend to the surface of the electrode. Alternatively, the silicon nitride film may be formed at the interface between the ferroelectric film 205 and the ferroelectric film 205 or the high dielectric constant oxide film. It may be. In this case, a ferroelectric film or a high-k oxide film is oxygen-annealed or oxygen-plasma-annealed to saturate oxygen, and then a silicon nitride film is formed on the surface to form a ferroelectric film or a high-k film. Without causing oxygen deficiency in the oxide film
This has the effect of preventing deterioration of characteristics due to oxygen deficiency due to the application of an electric field or the flow of a space charge limiting current.

FIG. 3 is a sectional view of a main part of a ferroelectric device according to another embodiment of the present invention. That is, the substrate 30
After the formation of the electrode 303 on the insulating film 302 on the substrate 1, a ferroelectric film 304 or a high dielectric constant oxide film is
m, and an electrode composed of the titanium nitride film 305 is formed to a thickness of 10 nm to 100
m thick, but the titanium nitride film 30
5 may be formed on or under the titanium nitride film 305 by laminating electrodes made of other metals or alloys.
03 may be an electrode having a titanium nitride film or a laminated structure of a titanium nitride film and another metal or alloy. Further, the phosphorus glass layer, the silicon nitride film, or a laminated film thereof as described in the above embodiments may be formed at the interface between the titanium nitride electrode and the ferroelectric film 304. In this case, a ferroelectric film or a high dielectric constant oxide film is subjected to oxygen annealing or oxygen plasma annealing to saturate oxygen, and then a titanium nitride electrode is formed on the surface to form a ferroelectric film or high dielectric constant film. There is an effect that characteristics deterioration due to oxygen deficiency due to application of an electric field or flow of a space charge limiting current can be prevented without causing oxygen deficiency in the oxide film.

FIG. 4 is a sectional view of a main part of a ferroelectric device showing still another embodiment of the present invention. That is, after the electrode 403 is formed on the insulating film 402 on the substrate 401, the ferroelectric film 404 or the high dielectric constant oxide film is
In this embodiment, two opposing electrodes 405 and 406 are formed so as to have a thickness of about nm and face the surface of the ferroelectric film 404 or the high dielectric constant oxide film. Instead, the counter electrodes 405 and 406 only need to be formed on one main surface of the ferroelectric film 404 or the high dielectric constant oxide film.
05 and 406 may be formed at the interface between the insulating film 402 and the ferroelectric film 404 or the high dielectric constant oxide film. Further, it is needless to say that the phosphorus glass layer, the silicon nitride film, the laminated film thereof, or the titanium nitride electrode shown in the above embodiments may be applied to the present embodiment. As described above, when the counter electrode is provided on one main surface of the ferroelectric film or the high-k oxide film, the interface treatment between each electrode and the ferroelectric film or the high-k oxide film becomes the same, and the interface state becomes high. The potential densities are also the same, and even if the polarity of the electrodes is changed, the symmetry of the electrical characteristics is improved, and there is an effect that the electrical characteristics can be stabilized.

It should be noted that the present invention is not limited to the planar ferroelectric devices shown in the embodiments and the like, but also to ferroelectric devices such as vertical ferroelectric devices, dynamic memory capacitor units and stand-alone ferroelectric capacitors. It is needless to say that the present invention can also be applied to the above.

[0015]

According to the present invention, it is possible to provide a ferroelectric device in which the electric characteristics of the ferroelectric are constant, the life is long, and the characteristics are stable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a ferroelectric device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a ferroelectric device according to another embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a ferroelectric device showing another embodiment of the present invention.

FIG. 4 is a sectional view of a main part of a ferroelectric device showing still another embodiment of the present invention.

[Explanation of symbols]

101, 201, 301, 401 ... substrate 102, 202, 302, 402 ... insulating film 103, 107, 203, 207, 303, 403 ...
-Electrodes 104, 106: Phosphor glass layer 105, 205, 304, 404: Ferroelectric film 204, 206: Silicon nitride film 305: Titanium nitride film 405, 406: Counter electrode

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[Procedure amendment]

[Submission date] July 26, 1999 (1999.7.2)
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

SUMMARY OF THE INVENTION The present invention relates to a ferroelectric device, and relates to a substrate, an insulating film formed on the substrate, a first electrode formed on the insulating film, and a first electrode. A ferroelectric film formed on the first electrode and a second electrode formed on the ferroelectric film, and at least one of the first and second electrodes Is made of a titanium nitride film. In the above description, a material made of a metal or an alloy different from the titanium nitride is provided on at least one of the titanium nitride film and the titanium nitride film.
Further, in any one of the above contents, a phosphor glass layer is interposed between the first or second electrode and the ferroelectric film. In addition, the first or the second
A silicon nitride film is interposed between the electrode and the ferroelectric film. In addition, the first or the second
A laminated film of a phosphorus glass layer and a silicon nitride film is interposed between the electrode and the ferroelectric film. Further, another ferroelectric device of the present invention is characterized in that an electrode made of a titanium nitride film is formed on the surface of the ferroelectric film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/8242

Claims (4)

[Claims] 1. A ferroelectric device comprising a phosphor glass layer formed on the surface of a ferroelectric film, or removing the phosphor glass layer after forming it. 2. A ferroelectric device comprising a silicon nitride film formed on a surface of a ferroelectric film. 3. A ferroelectric device characterized in that at least one or more electrodes made of a titanium nitride film are formed on the surface of the ferroelectric film. 4. A ferroelectric device characterized in that at least one main surface of a ferroelectric film is formed with two electrodes facing each other.