JP2000003997A - Dielectric element and semiconductor storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an oxygen depletion of a metal oxide dielectric in the vicinity of an electrode and lessen a film fatigue atmosphere or a leak current, by a method wherein oxygen is included in at least one of respective electrodes in a region in mutual opposition to the metal oxide dielectric thin film. SOLUTION: One electrode (a lower electrode) 203 of a capacity element is formed, for example, with platinum of 0.5 μm by a sputter method. Next, oxygen ions are injected to the lower electrode 203, and a region 204 including oxygen is formed on a surface of the lower electrode. Next, a PZT of 0.5 μm which is a ferroelectric metal oxide dielectric is formed as a dielectric film 205 by the sputter method, and as one more electrode (an upper electrode) 206 of the capacity element, for example, it is formed with platinum of 0.4 μm by the sputter method. Finally, oxygen ions are injected from a surface of the upper electrode 206 by an ion.doping method. At this time, the injected oxygen is set to reach near an interface between the upper electrode 206 and the dielectric film 205.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric element using a thin film having a metal oxide dielectric as a substrate and a method of manufacturing the dielectric element.

[0002]

2. Description of the Related Art In a dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a thin film made of a metal oxide dielectric as a substrate, a small-area large-capacitance element or a ferroelectric capacitance element is used. In order to obtain it, it is conventionally possible to use, for example, the Journal of Applied Physics (J. Appl.
Phys., 1991, Vol. 70, No. 1, pp. 382-388, as an electrode material, platinum (Pt), and as a dielectric material, a ferroelectric material having a perovskite crystal structure. PZT (Pb (Zr _x Ti _1-x ) O ₃ ) was used.

FIG. 3 shows an example of a dielectric element having a structure in which a ferroelectric substance and two electrodes are stacked on a silicon substrate. FIG.
In the figure, 301 is a silicon substrate, and 302 is an insulating layer of silicon dioxide (SiO ₂ ). Reference numeral 304 denotes a ferroelectric film using PZT, and a lower electrode 303 using platinum.
And an upper electrode 305 to form a capacitive element. 306 is an element protection film.

[0004]

As described above, the lower electrode 3
03, in the structure in which the ferroelectric film 304 and the upper electrode 305 are laminated, depending on the film forming conditions of the ferroelectric film 304, the cycle of the applied voltage for inverting the polarization is repeated, or the repetitive force is within the elastic limit. In this case, oxygen depletion occurs in the vicinity of the electrode of the ferroelectric film 304 so that ferroelectricity is no longer exhibited, or insulation failure occurs, and leakage current increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to prevent a metal oxide dielectric from being depleted of oxygen in the vicinity of an electrode and to reduce a film fatigue phenomenon and a leak current. It is to provide an element.

[0006]

In a dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a thin film having a metal oxide dielectric as a substrate, at least one of the electrodes is provided. A region in contact with the thin film having the metal oxide dielectric as a substrate, wherein oxygen is contained, and the metal oxide dielectric has a perovskite-type crystal structure, and is a metal oxide dielectric. And the electrode is mainly composed of one or more of a platinum group element and gold.

In a method of manufacturing a dielectric element having one or more electrodes in contact with a thin film having a metal oxide dielectric as a substrate, at least one of the electrodes is provided with oxygen ions. Or a step of exposing at least one of the electrodes to oxygen plasma or ozone plasma, and at least one of the electrodes And a step of exposing to oxygen plasma or ozone plasma while heating.

[0008]

FIG. 1 is a main sectional view showing one embodiment (hereinafter referred to as a first embodiment) of a dielectric element of the present invention. FIG. 2 shows one embodiment of a method for manufacturing a dielectric element according to the present invention (hereinafter, referred to as a “element”).
FIG. 9 is a main process sectional view showing a second embodiment).

First, a ferroelectric capacitor using a dielectric element according to the present invention will be described with reference to FIG. 1 for a first embodiment.

In FIG. 1, reference numeral 101 denotes a silicon substrate. Reference numeral 102 denotes an insulating layer serving as a base of the dielectric element. For example, the silicon substrate 101 is thermally oxidized to form 1 μm silicon dioxide (SiO ₂ ).

Reference numeral 103 denotes one electrode (hereinafter referred to as a lower electrode) of the capacitive element according to the gist of the present invention, which is formed, for example, by forming 0.5 μm of platinum by a sputtering method and then exposing it to, for example, oxygen plasma. Then, oxygen is implanted from the surface of the lower electrode 103 to form a region 104 containing oxygen.

Reference numeral 105 denotes a metal oxide dielectric, for example, a ferroelectric PLZT ((Pb _0.9 La _0.1 ) (Ti _0.6 Zr _0.4 )
O ₃ ) is formed to a thickness of 0.5 μm by a sol-gel method. 106
Is the other electrode of the capacitor (hereinafter referred to as the upper electrode)
For example, gold is formed in a thickness of 0.5 μm by a sputtering method. Reference numeral 107 denotes an element protection film formed of, for example, 1 μm silicon dioxide by a chemical vapor deposition method.

The above is a first embodiment of the present invention.

As in the prior art, the region 1 containing oxygen
04, the initial spontaneous polarization was 10 μC
/ Cm ² , the cycle of alternately applying +5 V and −5 V to the upper electrode and grounding the lower electrode is repeated 10 ⁵ times, resulting in ⁵ μC / cm ² , and a decrease in spontaneous polarization of 50%
there were. However, since the region 104 containing oxygen is formed on the surface of the lower electrode 103 as in the first embodiment of the present invention, even after a similar voltage cycle is applied,
Its spontaneous polarization was 8 μC / cm ² and the decrease in spontaneous polarization was 20%.

Next, with reference to FIG. 2, a description will be given of a dielectric element according to a second embodiment of the present invention and a ferroelectric capacitive element using the manufacturing method thereof according to the present invention.

In FIG. 2, reference numeral 201 denotes a silicon substrate. Reference numeral 202 denotes an insulating layer serving as a base of the dielectric element. For example, the silicon substrate 201 is thermally oxidized to form 1 μm silicon dioxide (SiO ₂ ). Reference numeral 203 denotes one electrode of a capacitor (hereinafter, referred to as a lower electrode) according to the gist of the present invention.
For example, 0.5 μm of platinum is formed by a sputtering method (FIG. 2A).

Next, for example, 30
Oxygen ions (O ₂ ⁺ ) accelerated at keV are implanted at a dose of 10 ¹²
Injection into the lower electrode 203 is performed at a density of cm ⁻² to form a region 204 containing oxygen on the surface of the lower electrode (FIG. 2B).

Next, as the dielectric film 205, for example, PZT (Pb (Ti _0.55 Zr _0.45 ) O ₃ ), which is a ferroelectric metal oxide dielectric having a perovskite crystal structure, is formed to a thickness of 0.5 μm by sputtering. Then, as another electrode (hereinafter referred to as an upper electrode) 206 of the capacitor, for example, platinum is formed to a thickness of 0.4 μm by sputtering (see FIG. 2).
(C)).

[0019] Finally, the ion doping method (ion implantation method that does not mass spectrometry), an acceleration oxygen ions _{^{100keV (O +, O 2 +}} , O 3 + etc.) the upper electrode 20
6 Inject from the surface. At this time, it is desirable to use oxygen ions accelerated to an energy of 60 keV or more so that the implanted oxygen reaches the vicinity of the interface between the upper electrode 206 and the dielectric film 205 (FIG. 2 (d)). .

The above is a second embodiment of the present invention.

As described above, when a region containing oxygen is formed in a region where the lower electrode 203 and the upper electrode 206 are in contact with the dielectric film 205, the initial spontaneous polarization is 20 μC /
cm ² , and 16 μC / cm ² after applying a voltage cycle of +5 V and −5 V 10 ⁵ times.
03 and the upper electrode 206 did not form an oxygen-containing region, the spontaneous polarization was initially 20 μC / c
m ² , 8 μC / cm ² after similar voltage cycling.

[0022]

As described above, according to the dielectric element of the present invention and the method of manufacturing the same, the spontaneous polarization is reduced or the leakage is reduced after the voltage or the stress is repeatedly applied to the dielectric element. An increase in current can be prevented, and a highly reliable ferroelectric element can be realized.

[Brief description of the drawings]

FIG. 1 is a main cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a main process of a second embodiment of the present invention.

FIG. 3 is a main sectional view of a dielectric element according to a conventional technique.

[Explanation of symbols]

 Reference Signs List 101 silicon substrate 102 insulating layer 103 lower electrode 104 region containing oxygen 105 dielectric film 106 upper electrode 201 silicon substrate 202 insulating layer 203 lower electrode 204 region containing oxygen 205 dielectric film 206 upper electrode 301 silicon substrate 302 insulating layer 303 Lower electrode 304 Dielectric film 305 Upper electrode 306 Device protection film

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[Procedure amendment]

[Submission date] July 9, 1999 (July 7, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Dielectric element and semiconductor memory device

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

According to the present invention, there is provided a dielectric element comprising:
In a dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a metal oxide dielectric thin film, oxygen is supplied to at least one of the electrodes in a region opposed to at least the metal oxide dielectric thin film. It is characterized by including. Further, in addition to the above, the metal oxide dielectric has a perovskite crystal structure.
Alternatively, the electrode is mainly composed of one or more of a platinum group element and gold. Alternatively, the metal oxide dielectric is PZT (Pb (Zr _x Ti
_1-x ) O ₃ ) and PLZT ((Pb _0.9 La _0.1 ) (Ti _0.6 Zr _0.4 )
O ₃ ).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

On the other hand, a semiconductor memory device of the present invention is characterized by using any one of the above-described dielectric elements.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 21/8242 21/8247 29/788 29/792

Claims (6)

[Claims] 1. A dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a thin film using a metal oxide dielectric as a substrate, wherein at least one of the electrodes has at least the metal oxide A dielectric element characterized by containing oxygen in a region in contact with a thin film having a dielectric as a substrate. 2. The dielectric element according to claim 1, wherein the metal oxide dielectric is a metal oxide dielectric having a perovskite crystal structure. 3. The dielectric element according to claim 1, wherein the electrode contains one or more of a platinum group element and gold as main components. 4. A method for manufacturing a dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a thin film using a metal oxide dielectric as a substrate, wherein at least one of the electrodes has an oxygen ion 2. The method for manufacturing a dielectric element according to claim 1, further comprising the step of implanting. 5. A method for manufacturing a dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a thin film using a metal oxide dielectric as a substrate, wherein at least one of the electrodes is made of oxygen plasma. 2. The method according to claim 1, further comprising a step of exposing the dielectric element to ozone plasma. 6. A method of manufacturing a dielectric element having a structure in which one or a plurality of electrodes are brought into contact with a thin film using a metal oxide dielectric as a substrate, wherein at least one of the electrodes is heated. 2. The method according to claim 1, further comprising a step of exposing to oxygen plasma or ozone plasma.