JP2000022083A - Mim capacitor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reduction of insulation breakdown voltage due to damage of dielectric film or forming a thinner film in a highly integrated MIM capacitor, by insulating a gap between a second electrode and the surface exposing over the dielectric film in its periphery in the end of the second electrode. SOLUTION: A second electrode 11 is formed by etching, and it is oxidized from its side wall by using an SiO2 film formed thereon as a mask so as to form an oxidization area 7. Thus, a gap between the second electrode 11 to be given a voltage and the surface of damaged dielectric film 3 is insulated, so that a leakage current can be prevented in an end 6 and the reduction of insulation breakdown voltage associated with the generation of damage area be also prevented. Therefore, the side wall of the second electrode 11 is oxidized to form an insulation film, thereby insulating a gap between the second electrode 11 and the surface exposing over the dielectric film and preventing the reduction of insulation breakdown voltage in the end part of the second electrode. As a result, the reliability even in a highly integrated thin-film MIM capacitor can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-dielectric-metal capacitor, and more particularly, to a metal-dielectric-metal capacitor having a high withstand voltage and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional structure of a metal-dielectric-metal (Metal-Insulator-Metal) capacitor (hereinafter referred to as "MIM").
Capacitor. " FIG. In the drawing, 1 is a semi-insulating GaAs substrate, 2 is a first electrode (lower electrode) made of, for example, Au, 3 is a dielectric film made of, for example, a silicon nitride film, and 11 is a second electrode (upper electrode) made of, for example, Au ). Generally, in a MIM capacitor used in a high frequency band, Au having a small electric resistivity is used as a material of the second electrode 11, and the formation of the second electrode 11 is performed by using a second electrode material laminated on the entire surface of the dielectric film 3. The layer is formed on the second electrode 11 by dry etching such as reactive ion etching (RIE) using a resist mask or ion milling.
This is performed by etching away the second electrode material layer other than the portion.

[0003]

In the case where the second electrode material layer is formed by etching and removing the second electrode material layer, the second electrode material layer is etched until the surface of the dielectric film below the second electrode material layer is exposed. . In such a dry etching step, the exposed dielectric film surface is also etched to some extent,
Due to the formation of the etching damage layer, the crystallinity of the dielectric film deteriorates, the leak current easily flows, and the thickness of the dielectric film becomes thinner than the region not etched,
The withstand voltage may be reduced. In particular, according to the knowledge of the inventor, in the case where the dielectric film is thinned and the area of the capacitor electrode is reduced with the increase in the degree of integration of the element, the decrease in the withstand voltage at the end 6 of the second electrode is reduced. In such a highly integrated MIM capacitor, it is necessary to prevent a decrease in withstand voltage at the end 6 of the second electrode. Therefore, an object of the present invention is to provide a highly integrated MIM capacitor in which a dielectric film is prevented from being reduced in dielectric breakdown voltage due to damage or thinning of the dielectric film.

[0004]

Means for Solving the Problems Accordingly, as a result of earnest study, the present inventors have made it possible to insulate the end of the second electrode between the second electrode and the exposed surface of the dielectric film on the periphery thereof, The present inventors have found that a decrease in withstand voltage can be significantly reduced, and have completed the present invention.

That is, the present invention provides a first electrode formed on a semiconductor substrate, a dielectric film formed so as to cover the first electrode, and a second film formed so as to cover the dielectric film. A second electrode material layer formed by dry etching into a predetermined shape;
An electrode, and the second electrode is laminated on the first electrode via the dielectric film, and the surface of the dielectric film is exposed around the second electrode by dry etching of the second electrode material. A MIM capacitor, wherein the second electrode and the exposed surface of the dielectric film exposed by dry etching are insulated.
When the second electrode is formed by dry etching, the surface of the dielectric film below the first electrode material layer is also etched, thereby forming a damaged layer or reducing the thickness of the dielectric film. Therefore, when the second electrode is in contact with the etched dielectric film surface, a leak current or the like is generated, and the dielectric strength of the capacitor is reduced. Thus, by insulating the second electrode from the exposed surface of the dielectric film to prevent the occurrence of such a leak current, it is possible to prevent a decrease in withstand voltage at the end of the second electrode. As a result, a highly integrated thin film MIM
Also in the capacitor, it is possible to prevent a decrease in the withstand voltage, to form a highly reliable MIM capacitor having good capacitor characteristics.

The present invention also provides that the second electrode has an insulating region oxidized inward from a side wall of the second electrode, and the insulating region allows the second electrode to be exposed to the exposed surface of the dielectric film. Is insulated from the MIM capacitor. As described above, the insulation between the second electrode and the exposed surface of the dielectric film is performed by using the insulating film oxidized inward from the side wall of the second electrode, so that the withstand voltage can be reduced with a simple structure. Can be prevented.

According to the present invention, the second electrode has a laminated structure of a lower metal electrode and an upper metal electrode, each of which is conductive, and the lower metal electrode is oxidized inward from a side wall thereof. An insulating region, and the second region is provided by the insulating region.
An MIM capacitor characterized in that an electrode is insulated from an exposed surface of the dielectric film. In particular, when an electrode material that is not easily oxidized is used, a second electrode is formed from a lower metal electrode that is easily oxidized and an upper metal electrode that is hardly oxidized, and only the lower metal electrode is oxidized to form a dielectric with the second electrode. Insulation between the exposed surface of the bodily membrane can be achieved.

The present invention also provides that the second electrode has a laminated structure of a lower metal electrode and an upper metal electrode, each of which is conductive, and the lower metal electrode is etched from a side wall thereof to thereby form the lower metal electrode. An MIM capacitor characterized in that a gap is provided between an electrode and an exposed surface of the dielectric film, and the second electrode and the exposed surface of the dielectric film are insulated from each other. When the selective etching of the lower metal electrode is easy, by lowering only the lower metal electrode, it is possible to prevent a decrease in dielectric strength with a simple structure.

Preferably, the upper metal electrode is made of Au or Pt. This is because high-frequency characteristics can be improved by using Au or Pt having a small electric resistivity for the upper metal electrode.

The present invention also provides a first electrode formed on a semiconductor substrate, a dielectric film formed so as to cover the first electrode, and a lower metal layer formed so as to cover the dielectric film. An electrode material layer; and an upper metal electrode formed by dry-etching the upper metal material layer formed to cover the lower metal material layer into a predetermined shape. The dielectric film is formed on the first electrode. A capacitor in which the upper metal electrode is stacked with the lower electrode material layer interposed therebetween, wherein the lower metal material layer excluding a lower portion of the upper metal electrode is oxidized to an insulating layer,
The MIM capacitor is characterized in that the lower metal material layer surrounded by the insulating layer is a lower metal electrode, and a second electrode is formed from the lower metal electrode and the upper metal electrode.
In such a structure, the second electrode (upper metal electrode) is formed by dry etching in a state where the surface of the dielectric film is covered with the lower electrode material. It is possible to prevent a decrease in dielectric strength.

It is preferable that the second electrode is formed inside a region above the first electrode. With this structure, the capacitance of the capacitor can be adjusted only by changing the electrode area of the second electrode.

According to the present invention, a first electrode is formed on a semiconductor substrate, a dielectric film and a second electrode material layer are sequentially formed so as to cover the first electrode, and the second electrode material layer is etched. Forming a second electrode above the first electrode and removing the second electrode material layer other than the second electrode to expose a surface of the dielectric film, the method comprising: A method of manufacturing a MIM capacitor, comprising an insulating step of insulating the second electrode and the exposed surface of the exposed dielectric film after forming the second electrode. By providing such an insulating step, it becomes possible to manufacture an MIM capacitor in which a leak current or the like between the second electrode and the exposed surface of the dielectric film is prevented.

The present invention is also a method for manufacturing an MIM capacitor, wherein the insulating step is a step of oxidizing the second electrode inward from a side wall to provide an insulating region. By using such a method, the insulating region can be formed in a simple process.

Further, in the present invention, the insulating step preferably comprises forming the second electrode material layer by laminating a lower metal material layer and an upper metal material layer, each of which is conductive. The MIM capacitor is characterized by a step of oxidizing a lower metal electrode formed by etching a metal layer from a side wall to an inward direction to provide an insulating region. By using such a method, the insulating region can be formed by a simple process even when a material such as Au which is hardly oxidized is used as the upper metal material.

Further, in the present invention, in the insulating step, the second electrode material layer is formed by laminating a lower metal material layer and an upper metal material layer, each of which is conductive. A method of manufacturing a MIM capacitor, comprising: etching a lower metal electrode formed by etching a metal layer inward from a side wall to provide an interval between the lower metal electrode and an exposed surface of the dielectric film. But also. Even if such a method is used, the formation of the insulating region can be performed by a simple process when a material that is not easily oxidized such as Au is used as the upper metal material.

Further, according to the present invention, a first electrode is formed on a semiconductor substrate, and a dielectric film and a second electrode material layer are sequentially formed so as to cover the first electrode. A method of manufacturing a capacitor, wherein a second electrode is formed above the first electrode by dry etching through the dielectric film,
The second electrode material layer is formed by laminating a lower metal material layer and an upper metal material layer, each of which is conductive, and dry-etching the upper metal material layer to form an upper metal electrode. After removing the upper metal material layer other than the upper metal electrode to expose the surface of the lower metal material layer, the lower metal material layer other than the lower portion of the upper metal electrode is oxidized to be insulated. M is characterized in that the lower metal material layer below the upper metal electrode is used as a lower metal electrode, and a second electrode composed of the upper metal electrode and the lower metal electrode is formed.
It is also a method of manufacturing an IM capacitor. By using such a method, since the surface of the dielectric film is not dry-etched, formation of a damaged region can be prevented, and it is possible to manufacture an MIM capacitor in which a decrease in the withstand voltage of the capacitor is prevented.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view of the MIM capacitor according to the present embodiment, in which the same reference numerals as those in FIG. 9 denote the same or corresponding parts. That is, 1 is a semi-insulating GaAs substrate, and 2 is, for example, A
A first electrode (lower electrode) made of u, 3 is a dielectric film made of, for example, a silicon nitride film, 6 is an end of the second electrode, 7 is an oxidized region formed by oxidizing the second electrode, and 11 is, for example, A
1 is a second electrode (upper electrode).

As described above, when the second electrode 11 is formed by using, for example, RIE or the like, the upper surface of the dielectric film 3 is also etched to form a damaged layer on the surface, or the thickness of the dielectric film itself. Or become thin. In the MIM capacitor having the conventional structure shown in FIG. 9, since the second electrode 11 and the surface of the dielectric film having the damaged layer are adjacent to each other, when a voltage is applied between the first electrode 2 and the second electrode 11, , Second
Leakage current occurs at the end 6 of the electrode 11 and the MIM
The dielectric strength of the capacitor will be reduced. Therefore,
In the present embodiment, the second electrode is oxidized from the side wall, and the periphery of the second electrode is oxidized to insulate the second electrode from the exposed surface of the dielectric film 3, thereby preventing the occurrence of a leak current and the like. Preventing. Specifically, after the second electrode 11 is formed by etching, the second electrode 11 is oxidized from the side wall using a SiO ₂ film (not shown) formed on the second electrode 11 as a mask, and the oxidized region 7 is formed. To form As a result, insulation is provided between the second electrode 11 to which the voltage is applied and the damaged dielectric film 3 surface, thereby preventing the occurrence of a leak current at the end 6 and the like, and the dielectric strength with the occurrence of the damaged region. Can be prevented from decreasing.

In Japanese Unexamined Patent Publication No. 5-72570, in order to prevent the occurrence of a leak or the like particularly at the edge of the first electrode (lower electrode) 2, the dielectric film is oxidized to be insulated and the leak or the like is reduced. Methods to prevent this have been proposed. Such a method may be applied to the end 6 of the second electrode (upper electrode) 11. However, in such a method, the dielectric film itself is oxidized. It is necessary to form a dielectric film having a high content (that is, a low oxygen content). Therefore, the dielectric constant of the dielectric film cannot be optimized according to the element design, and there is a disadvantage that the improvement of the characteristics of the MIM capacitor is limited.

FIG. 2 shows another MIM capacitor structure according to this embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. In the MIM capacitor of FIG.
Is formed from the lower metal electrode 4 and the upper metal electrode 5, and the insulating region 4 is formed only on the side wall of the lower metal electrode 4.
Is formed.

When the MIM capacitor is used as a high-frequency element, it is preferable to use low-resistance Au or the like as an electrode material of the first and second electrodes. Where Au
Is very hard to be oxidized, so that it is difficult to oxidize the side wall of the second electrode to form the oxide layer 4. Therefore, in such a case, the second electrode is formed of the lower metal electrode 4 that is easily oxidized and the upper metal electrode 5 that is low in resistance and hardly oxidized, and the oxidized region 7 is formed on the side wall of the lower metal electrode 4. The second electrode and the exposed surface of the dielectric film 3 are insulated.

A specific manufacturing method will be described with reference to FIGS. First, as shown in FIG.
Forming a first electrode material layer made of Au on an As substrate 1;
The first electrode 2 is formed by etching using a photolithography technique. Next, a silicon nitride film 3 having a thickness of, for example, 2000 .ANG.
To form Next, Ti as a material of the lower metal electrode 4 is formed by sputtering at, for example, 500 °, and Au as a material of the upper metal electrode 5 is formed by sputtering, for example, at 600 °.
0 ° is formed. Next, a resist mask 8 is formed on the upper metal material layer, and using the mask as a mask, the upper electrode material layer and the lower electrode material layer are etched by a dry etching method such as reactive ion etching or ion milling.

FIG. 4 is a cross-sectional view after etching the upper electrode material layer and the lower electrode material layer.
A second electrode is formed from the upper metal electrode 5. In this etching step, since the lower electrode material layer is etched until the surface of the dielectric film 3 is exposed, a damage layer is formed on the surface of the dielectric film 3 or the thickness of the dielectric film 3 is reduced. In particular, the withstand voltage decreases at the end 6 of the second electrode. The material of the lower metal electrode 4 is T
In addition to i, Al, Cu, or the like can be used, and as the material of the upper metal electrode 5, Pt or the like can be used in addition to Au. In the present embodiment, since the lower metal electrode 4 is thinner than the upper metal electrode 5,
Even if Ti or the like having a higher resistivity than u or the like is used for the lower metal electrode, the entire second electrode can have a sufficiently low resistance.

In the present embodiment, subsequently, as shown in FIG. 5, the lower metal electrode 4 is oxidized from the side walls, for example, by performing an oxygen plasma treatment to form an oxidized region 7. Specifically, Ti constituting the lower metal electrode 4 is oxidized to form an insulating oxide region 7 made of TiO.

As described above, the oxidized region 7 is formed and the second region is formed.
By insulating between the electrode and the exposed surface of the dielectric film 5, a large voltage is not applied to the damaged region of the dielectric film 5, so that a decrease in the dielectric strength of the MIM capacitor can be prevented.

Further, the second electrode 11 (the lower metal electrode 4 and the upper metal electrode 5) is formed so as to be located inside the first electrode 2, in other words, the second electrode 11 is formed smaller than the first electrode 2. Accordingly, the capacitance of the MIM capacitor can be changed only by changing the area of the second electrode 11.

Embodiment 2 FIG. A second embodiment of the present invention will be described with reference to FIG. In the drawing, the same reference numerals as those in FIG. 2 indicate the same or corresponding portions, and 9 indicates an etching-off region. The MIM capacitor shown in FIG. 6 uses, for example, a diluted hydrofluoric acid solution instead of oxidizing the side wall of the lower metal electrode 4 after performing the steps of FIGS. Etching is removed by about 300 ° to form an etching off region 9. In this etching step, the upper metal electrode 5 made of Au is not etched, and only the side wall portion of the lower metal electrode 4 made of Ti is selectively etched. As a result, a gap is provided between the second electrode and the exposed surface of the dielectric film 6 on which the damaged layer is formed, and a decrease in the withstand voltage at the second electrode end 6 can be prevented.

Embodiment 3 A third embodiment of the present invention will be described with reference to FIGS. In the figure, the same reference numerals as those in FIG.
Indicates an oxidized region. In the MIM capacitor shown in FIG. 7, after the resist mask 8 is formed in the step shown in FIG. 3 of the first embodiment, only the upper electrode material layer made of Au is formed by a dry etching method such as reactive ion etching or ion milling. Dry-etch. In this etching step, no damage layer is formed on the surface of the dielectric film 3 because the surface of the dielectric film 3 is not exposed.

Next, as shown in FIG.
Is used as a mask to oxidize the lower electrode material layer made of Ti except for the lower region of the upper metal electrode 5 to form TiO.
And Thus, the lower region of the upper metal electrode 5 is not oxidized, and becomes the lower metal electrode 4 made of Ti.

As described above, the MIM according to the present embodiment
In the capacitor, the surface of the dielectric film 4 is not etched and a damaged region is not formed.
It is possible to prevent a decrease in withstand voltage at the electrode end 6.

[0031]

As is apparent from the above description, according to the present invention, by oxidizing the side wall of the second electrode to form an insulating layer, the second electrode and the exposed surface of the dielectric film can be separated. The insulation between the electrodes can prevent the lowering of the withstand voltage at the end of the second electrode.

As a result, even in a highly integrated thin-film MIM capacitor, it is possible to form a highly reliable MIM capacitor which prevents a decrease in withstand voltage, has good capacitor characteristics, and has high reliability.

According to the present invention, the second electrode is formed from the lower metal electrode and the upper metal electrode, and only the side wall of the lower metal electrode is oxidized to form an insulating layer. Even if a material that is hardly oxidized is used as the material of the upper metal electrode by etching only the side wall of the second electrode to form an etching off region, the insulation between the second electrode and the exposed surface of the dielectric film is maintained. Thus, it is possible to prevent a decrease in the withstand voltage at the end of the second electrode.

According to the present invention, the second electrode can be formed without exposing the surface of the dielectric film.
It is possible to prevent formation of a damaged region on the dielectric film that occurs with the formation of the electrode, and to prevent a decrease in withstand voltage at the end of the second electrode.

Further, according to the present invention, a relatively simple insulating step is added to the conventional MIM capacitor manufacturing process or only a part of the conventional manufacturing process is improved.
It is possible to prevent a decrease in the dielectric strength of the MIM capacitor, and to manufacture a highly reliable MIM capacitor at low cost and easily.

[Brief description of the drawings]

FIG. 1 is a sectional view of an MIM capacitor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the MIM capacitor according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing the manufacturing process of the MIM capacitor according to the first embodiment of the present invention;

FIG. 4 is a sectional view showing the manufacturing process of the MIM capacitor according to the first embodiment of the present invention;

FIG. 5 is a sectional view showing the manufacturing process of the MIM capacitor according to the first embodiment of the present invention.

FIG. 6 is a sectional view of an MIM capacitor according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a manufacturing process of the MIM capacitor according to the third embodiment of the present invention;

FIG. 8 is a sectional view of the manufacturing process of the MIM capacitor according to the third embodiment of the present invention.

FIG. 9 is a cross-sectional view of a conventional MIM capacitor.

[Explanation of symbols]

1 semi-insulating GaAs substrate, 2 first electrode (lower electrode),
3 dielectric film, 4 lower metal electrodes, 5 upper metal electrodes,
6 end of second electrode, 7 oxidized region, 8 resist mask, 9 etching-off region, 10 oxidized region, 11
Second electrode (upper electrode).

Claims (12)

[Claims] A first electrode formed on a semiconductor substrate;
A dielectric film formed so as to cover the first electrode, and a second electrode formed by dry-etching a second electrode material layer formed so as to cover the dielectric film into a predetermined shape; A capacitor in which the second electrode is laminated on the first electrode via the dielectric film, and the surface of the dielectric film is exposed around the second electrode by dry etching of the second electrode material; A MIM capacitor, wherein the second electrode and the exposed surface of the dielectric film exposed by dry etching are insulated. 2. The semiconductor device according to claim 1, wherein the second electrode has an insulating region oxidized inward from a side wall of the second electrode, and the insulating region insulates the second electrode from an exposed surface of the dielectric film. The MIM capacitor according to claim 1, wherein: 3. The second electrode has a laminated structure of a lower metal electrode and an upper metal electrode, each of which is conductive, and the lower metal electrode has an insulating region oxidized inward from a side wall thereof. 2. The MIM capacitor according to claim 1, wherein the insulation region insulates the second electrode from the exposed surface of the dielectric film. 4. The second electrode has a laminated structure of a lower metal electrode and an upper metal electrode, each of which is conductive, and the lower metal electrode and the dielectric material are etched by etching the lower metal electrode from a side wall thereof. 2. The MIM capacitor according to claim 1, wherein an interval is provided between the exposed surface of the body film and the second electrode and the exposed surface of the dielectric film are insulated. 5. The MIM capacitor according to claim 3, wherein the upper metal electrode is made of Au or Pt. 6. A first electrode formed on a semiconductor substrate,
A dielectric film formed to cover the first electrode; a lower metal electrode material layer formed to cover the dielectric film; and an upper metal material layer formed to cover the lower metal material layer And an upper metal electrode formed by dry-etching into a predetermined shape. The upper metal electrode is laminated on the first electrode via the dielectric film and the lower electrode material layer. The lower metal material layer excluding the lower part of the upper metal electrode is oxidized to form an insulating layer; the lower metal material layer surrounded by the insulating layer is formed as a lower metal electrode; the lower metal electrode and the upper metal MIM characterized by forming a second electrode from an electrode
Capacitors. 7. The MIM capacitor according to claim 1, wherein said second electrode is formed inside a region above said first electrode. 8. A first electrode is formed on a semiconductor substrate, a dielectric film and a second electrode material layer are sequentially formed so as to cover the first electrode, and the second electrode material layer is dry-etched. Forming a second electrode above the first electrode by removing the second electrode material layer other than the second electrode, thereby exposing the surface of the dielectric film. A method for manufacturing a MIM capacitor, comprising an insulating step of insulating between the second electrode and the exposed surface of the exposed dielectric film after forming the second electrode. 9. The method according to claim 8, wherein the insulating step is a step of oxidizing the second electrode inward from a side wall to provide an insulating region. 10. The insulating step, wherein the second electrode material layer is formed by laminating a lower metal material layer and an upper metal material layer, each of which is conductive, and etching the lower metal material layer. 9. The method according to claim 8, further comprising a step of oxidizing the formed lower metal electrode inward from the side wall to provide an insulating region. 11. The insulating step comprises forming the second electrode material layer by laminating a lower metal material layer and an upper metal material layer, each of which is conductive, and etching the lower metal material layer. 9. A step of etching the formed lower metal electrode inward from the side wall to provide a space between the lower metal electrode and the exposed surface of the dielectric film.
3. The method for manufacturing an MIM capacitor according to item 1. 12. A first electrode is formed on a semiconductor substrate, a dielectric film and a second electrode material layer are sequentially formed so as to cover the first electrode, and the second electrode material layer is dry-etched. Forming a second electrode above the first electrode via the dielectric film, wherein the second electrode material layer is formed of a conductive lower metal material layer and an upper conductive metal layer. The upper metal material layer is formed by laminating the lower metal material layer, and the upper metal material layer is dry-etched to form an upper metal electrode, and the upper metal material layer other than the upper metal electrode is removed to form the lower metal material layer. After exposing the surface, the lower metal material layer except the lower portion of the upper metal electrode is oxidized and insulated to make the lower metal material layer below the upper metal electrode a lower metal electrode, and the upper metal electrode Forming a second electrode composed of the lower electrode and the lower metal electrode M characterized by Rukoto
A method for manufacturing an IM capacitor.