JPH0613545A - Ferroelectric device - Google Patents

Abstract

PURPOSE:To obtain constant electric characteristics of ferroelectric and prolong the life and stabilize the characteristics, by forming a phosphorus glass layer on the surface of a ferroelectric film or removing the phosphorus glass layer after forming the layer. CONSTITUTION:An insulating film 102 is formed on the surface of a substrate 101 made of semiconductor, etc., and an electrode 103 made of titanium-platinum or platinum, etc., is formed on the insulating film 102, and a ferroelectric film 105 is formed on the electrode 103. Then, a phosphorus glass layer 106 is formed on the surface of the ferroelectric film 105 or the phosphorus glass layer 106 is removed after forming the layer 106. Further, two electrodes 103 and 107 with the electrodes opposed each other are formed on at least one main surface of the ferroelectric film 105. The phosphorus glass layer 106 catches an alkali metal mobile ion in an oxide ferroelectric or a material having a high permittivity, and the layer 106 prevents the deterioration of characteristics and has an effect of a stabilization of the characteristics.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the structure of ferroelectric devices.

[0002]

2. Description of the Related Art Conventionally, a ferroelectric device has been formed as follows. That is, it has been customary that metal electrodes facing each other are formed on the two main surfaces of the ferroelectric film.

[0003]

However, according to the above-mentioned conventional technique, alkali such as sodium in the ferroelectric film is not formed.
Due to the movement of ions such as ions due to the electric field, the segregation accompanying the movement of the constituent elements such as oxygen and titanium, which are ferroelectric constituent elements due to the electric field, and the difference in the interface state between the electrode and the ferroelectric, There have been problems in stability of the characteristics such as the problem that the electric characteristics of the dielectric are not constant and the problem that the life is short.

It is an object of the present invention to provide a new ferroelectric device structure which solves the problems of the prior art.

[0005]

In order to solve the above problems and achieve the above objects, the present invention relates to a ferroelectric device, which comprises (1) forming a phosphorus glass layer on the surface of a ferroelectric film, or
Alternatively, removing the phosphorous glass layer after forming it, (2) forming a silicon nitride film on the surface of the ferroelectric film, and (3) forming an electrode made of at least one titanium nitride film on the surface of the ferroelectric film. And (4) at least one main surface of the ferroelectric film is formed with two electrodes facing each other.

[0006]

The phosphorous glass layer has a function of trapping mobile ions of alkali metal in the oxide ferroelectric substance or high-dielectric constant substance, preventing deterioration of the characteristic, and stabilizing the characteristic.

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

The titanium nitride electrode is an electric field application or space charge limiting current of a constituent element of the oxide ferroelectric or high dielectric constant such as titanium or oxygen under the electrode provided on the oxide ferroelectric or high dielectric constant. It has the effect of preventing segregation due to and stabilizing the characteristics.

By providing a counter electrode on one main 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 improved. They can be the same, and have the effect of preventing changes in characteristics due to polarity inversion.

[0010]

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

FIG. 1 is a sectional view of the main part of a ferroelectric device showing 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 the 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), lead, lanthanum, zirconium, titanium oxide (PLZT), or a ferroelectric film 105 such as barium titanate, or a high dielectric constant oxide film such as tantalum oxide or titanium oxide, which is formed to a thickness of 10 nm by sputtering deposition or the like.
When forming a film with a thickness of ~ 300 nm, CV
Phosphorous glass in which phosphorus oxide is mixed with silicon oxide formed by the D method, or the ferroelectric film 105 or the high dielectric constant oxide film is formed, and then phosphorus ions are implanted to form the ferroelectric film 10.
5 or 4 mol by converting the high-k oxide film to phosphorus glass
The phosphorus glass layer 103 having a phosphorus concentration of about 10% is formed to a thickness of about 10 nm, and even after the ferroelectric film 105 or the high dielectric constant oxide film is formed, the phosphorus glass layer 106 is formed by the same method as described above. The 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, and the phosphor glass layer 103 is formed. The phosphorous glass layer 106 may be omitted once, and then the mobile glass may be removed after the mobile ions are captured.
3 or 106 may be formed to extend to the side surface of the ferroelectric film 105, and the phosphor glass layer or the like may be not only a phosphor glass single layer but also a multilayer structure with titanium oxide, silicon oxide or the like. Good. Thus, when the phosphorus glass layer is formed on the surface of the ferroelectric film or the high dielectric constant oxide film, the phosphorus glass layer traps the mobile ions in the ferroelectric film or the high dielectric constant oxide film, There is an effect that the characteristic deterioration of the ferroelectric film or the high dielectric constant oxide film due to mobile ions can be prevented and the characteristics can be stabilized. FIG. 2 is a sectional view of a main part of a ferroelectric device showing another embodiment of the present invention. That is, the substrate 2
01, the electrode 203 is formed on the insulating film 202 formed on the insulating film 202, and the silicon nitride film 204 is formed to a thickness of 10 nm by the CVD method or the like.
˜50 nm thick, then a ferroelectric film 205 or 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.
To a thickness of about 10 nm to 50 nm, and then the electrode 20
7 is formed, the silicon nitride film 203 or 206 may be formed to extend to the side surface of the ferroelectric film 205. Alternatively, the silicon nitride film 203 or 206 may be formed of the ferroelectric material of the electrode 203 or 206. Body membrane 20
5 or on the surface or side surface excluding the interface with the high dielectric constant oxide film, or in this case, extending to the electrode surface. Further, the phosphorus glass layer of the above-described embodiment is formed on the silicon nitride film 204. Alternatively, it may be formed at the interface between 206 and the ferroelectric film 205 or the high-dielectric-constant oxide film, and the silicon nitride film is not only a silicon nitride film single layer but also a multi-layer film structure of a silicon oxide film or a titanium oxide film. May be In this case, if a ferroelectric film or a high-dielectric-constant oxide film is annealed with oxygen or oxygen plasma / annealed to saturate oxygen and then a silicon nitride film is formed on the surface, the ferroelectric film or the high-dielectric constant film is formed. Without causing oxygen deficiency in the oxide film,
There is an effect that it is possible to prevent characteristic deterioration due to oxygen deficiency due to application of an electric field or flow of a space charge limiting current.

FIG. 3 is a sectional view of a main part of a ferroelectric device showing another embodiment of the present invention. That is, the substrate 30
After the electrode 303 is formed on the insulating film 302 on the first dielectric film 304, a ferroelectric film 304 or a high dielectric constant oxide film is formed to a thickness of 10 nm to 300 n.
The thickness of the titanium nitride film 305 is about 10 nm to 100 n by a CVD method or a sputter deposition method.
The titanium nitride film 30 has a thickness of about m
5 or below the titanium nitride film 305 may be formed by laminating electrodes made of another metal or alloy.
Reference numeral 03 may also be an electrode having a laminated structure of a titanium nitride film or a titanium nitride film and another metal or alloy. Furthermore, the phosphorous glass layer, the silicon nitride film, or a laminated film thereof shown in the above-described embodiments may be formed at the interface between the titanium nitride electrode and the ferroelectric film 304. In this case, if a titanium nitride electrode is formed on the surface of the ferroelectric film or high dielectric constant oxide film by oxygen annealing or oxygen plasma annealing to saturate the oxygen, the ferroelectric film or high dielectric constant There is an effect that it is possible to prevent characteristic deterioration due to oxygen deficiency due to application of an electric field or flow of a space charge limiting current 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 forming the electrode 403 on the insulating film 402 on the substrate 401, a ferroelectric film 404 or a high dielectric constant oxide film is formed in a thickness of 5 nm to 300 nm.
The two electrodes 405 and 406 are formed so as to have a thickness of about 10 nm and face the surface of the ferroelectric film 404 or the high dielectric constant oxide film, but the electrode 403 is not always necessary. Instead, the counter electrodes 405 and 406 may be formed on one main surface of the ferroelectric film 404 or the high dielectric constant oxide film, that is, the counter electrode 4
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 goes without saying that the phosphorus glass layer, the silicon nitride film, the laminated film thereof, or the titanium nitride electrode shown in the above-mentioned embodiments may be applied to this embodiment. In this way, when the counter electrode is provided on one main surface of the ferroelectric film or the high dielectric constant oxide film, the interface treatment between each electrode and the ferroelectric film or the high dielectric constant oxide film becomes the same, and the interface The unit densities are also the same, and even if the polarity of the electrode is changed, the symmetry of the electric characteristics becomes good, and there is an effect that the electric characteristics can be stabilized.

The present invention is not limited to the planar type ferroelectric device shown in the embodiments and the like, but may be a vertical type ferroelectric device, a ferroelectric memory device such as a capacitor portion of a dynamic memory or an independent type ferroelectric capacitor. It goes without saying that it can also be applied to etc.

[0015]

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

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a ferroelectric device showing an embodiment of the present invention.

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

FIG. 3 is a cross-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 ...
Electrode 104, 106 ... Phosphorous glass layer 105, 205, 304, 404 ... Ferroelectric film 204, 206 ... Silicon nitride film 305 ... Titanium nitride film 405, 406 ... Counter electrode

Claims (4)

[Claims] 1. A ferroelectric device characterized in that a phosphor glass layer is formed on the surface of a ferroelectric film, or is formed and then removed. 2. A ferroelectric device characterized in that a silicon nitride film is formed on the surface of the ferroelectric film. 3. A ferroelectric device characterized in that at least one portion of an electrode made of a titanium nitride film is 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.