JP2003218219A - Semiconductor capacitor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor capacitor with a high withstand voltage obtained by laminating a lower electrode, a dielectric film and an upper electrode, with which current leakage can be prevented from generating between the upper and the lower electrodes, and to provide a method of manufacturing the same. <P>SOLUTION: A lower electrode 3 is formed on a semiconductor substrate 2. A first insulating film 4 having a hole is formed on the lower electrode 3. A dielectric film 5 is formed in a depressed shape on the lower electrode 3 and the first insulating film 4. Furthermore, a second insulating film 6 is selectively formed on a sidewall of the depressed portion of the dielectric film 5. An upper electrode 7 is formed so as to cover the dielectric film 5 and the second insulating film 6. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element such as a planar IC, and more particularly to a structure of a semiconductor capacitor formed on a substrate together with a transistor element and a manufacturing method thereof.

[0002]

2. Description of the Related Art Most of semiconductor capacitors in a planar type IC are of a MIM (Metal Insulator Metal) type. This MIM type capacitor is a MIS (Metal Ins
Since it is easier to design a capacitor electrode structure with a lower resistance than that of a semiconductor (SemiconductorSemiconductor) type, it is often used in semiconductor devices that require high-speed operation capacitance. In addition, the MIM type semiconductor capacitor has a low rate of change in capacitance due to voltage and temperature and has stable electrical characteristics, and is therefore often used in precision analog semiconductor devices.

FIG. 4 is a diagram showing a method of manufacturing a conventional MIM type semiconductor capacitor 41. Semiconductor capacitor 41
4A, first, as shown in FIG. 4A, a lower electrode 43 made of a metal such as Pt is formed on a semiconductor substrate 42 such as silicon by a DC sputtering method, and an ion using a rare gas such as Ar is used. Pattern by milling. Then, as shown in FIG. 4B, SiO 2 is formed on the lower electrode 43.
An interlayer insulating film 44 such as _{2 is} formed by a CVD method, and holes are formed by plasma etching using a reactive gas. Then, as shown in FIG.
After the dielectric film 45 such as SrTiO ₃ is formed on the interlayer insulating film 44 by the ion beam sputtering method, P
The upper electrode 46 such as t is formed by the DC sputtering method. Finally, as shown in FIG. 4D, the dielectric film 45 and the upper electrode 46 are simultaneously patterned by ion milling using a rare gas such as Ar to obtain the semiconductor capacitor 41.

[0004]

However, the conventional semiconductor capacitor 41 has the following problems. As shown in FIG. 4C, when the dielectric film 45 is formed on the lower electrode 43 and the interlayer insulating film 44, the film thickness of the dielectric film 45 at the bottom of the hole sidewall of the interlayer insulating film 44 is different. There is a problem that it is formed thinner than the part.
This is because when a hole is formed in the interlayer insulating film 44 by plasma etching, a processing residue is generated on the side wall of the resist serving as a mask, and a convex shape is formed around the processing pattern even after the resist is removed, and the dielectric film 45. This is because the step coverage is deteriorated when the film is formed by a physical film forming method such as an ion beam sputtering method.

As shown in FIG. 5 in which the portion B of FIG. 4D is enlarged, when the film thickness of the dielectric film flat portion 45a is 100, the film thickness of the dielectric film side wall bottom portion 45b is from 60 to 70. Become thin. Therefore, the electric field applied to this portion is locally increased, which increases the leak current and causes the breakdown voltage of the semiconductor capacitor 41 to decrease. Further, the above-mentioned problem also increases the leak current as the electrode interval, that is, the film thickness of the dielectric film 45 is reduced in order to increase the capacitance of the semiconductor capacitor 41.

An object of the present invention is to provide a semiconductor capacitor in which a lower electrode, a dielectric film and an upper electrode are laminated, and which has a high withstand voltage in which a leak current does not occur between the upper and lower electrodes and a manufacturing method thereof. It is in.

[0007]

In order to achieve the above object, a semiconductor capacitor of the present invention has a lower electrode, a dielectric film and an upper electrode on a semiconductor substrate or an insulating film formed on the semiconductor substrate. In the laminated semiconductor capacitor, the dielectric film is formed in a concave shape on the lower electrode, and the insulating film is formed on the side wall of the concave portion of the dielectric film.

The method of manufacturing a semiconductor capacitor according to the present invention comprises a step of forming a lower electrode on a semiconductor substrate or an insulating film formed on the semiconductor substrate, and a first insulating film on the semiconductor substrate including the lower electrode. And forming a hole in a portion of the first insulator film above the lower electrode, and forming a concave portion of the dielectric film on the lower electrode and the first insulator film exposed in the hole of the first insulator film. A step of forming, a step of forming a second insulator film on the side wall of the dielectric film recess, a step of forming the dielectric film and the second
The method is characterized by including a step of forming an upper electrode on the insulator film.

According to the semiconductor capacitor of the present invention, the second insulator film is formed on the side wall of the recess of the dielectric film formed on the lower electrode, and the thinned portion of the dielectric film is the second insulator. Since it is covered with the film, the leak current component flowing through the dielectric film is suppressed, and a semiconductor capacitor having a high withstand voltage can be provided.

Further, according to the method of manufacturing a semiconductor capacitor of the present invention, since the second insulating film can be selectively formed on the side wall of the concave portion of the dielectric film by anisotropic etching, the second insulating film can be stably manufactured with high yield. it can.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor capacitor according to an embodiment of the present invention will be described below with reference to FIGS.

1A and 1B are a sectional view and an enlarged sectional view of an essential part of a semiconductor capacitor 1 according to an embodiment of the present invention. As shown in FIG. 1A, in a semiconductor capacitor 1 of the present invention, a lower electrode 3 is formed on a semiconductor substrate 2, a first insulating film 4 having holes is formed on the lower electrode 3, and the lower electrode 3 is formed. A dielectric film 5 is formed in a concave shape on the first insulating film 3 and the first insulating film 4. Further, the second insulating film 6 is selectively formed on the side wall of the concave portion of the dielectric film 5, and the upper electrode 7 is formed so as to cover the dielectric film 5 and the second insulating film 6.
Are formed.

A method of manufacturing the semiconductor capacitor 1 will be described with reference to FIG. First, as shown in FIG. 2A, a lower electrode 3 made of Pt is formed on a semiconductor substrate 2 made of silicon by a DC sputtering method, and patterned by ion milling using a rare gas such as Ar. Further, a first insulator film 4 made of SiO ₂ for insulating between elements is formed so as to cover the entire patterned lower electrode 3 by C.
After forming by the VD method, holes are formed by dry etching using a reaction gas. Next, as shown in FIG. 2B, a dielectric film 5 made of SrTiO _{3 is} formed by an ion beam sputtering method, and then a second insulator film 6 made of Si ₃ N _{4 is} formed so as to cover the entire surface of the dielectric film 5. Are formed by the CVD method. Then, as shown in FIG.
By anisotropic etching such as the E method, only the horizontal surface of the second insulating film 6 is selectively etched, and the second insulating film 6 is left only on the side wall of the concave portion of the dielectric film 5. Then, FIG. 2 (d)
The upper electrode 7 made of Pt is formed on the dielectric film 5 and the second insulating film 6 by the DC sputtering method as shown in FIG. Finally, as shown in FIG. 2E, the dielectric film 5 and the upper electrode 7 are simultaneously patterned by ion milling using a rare gas such as Ar to obtain the semiconductor capacitor 1.

The semiconductor capacitor 1 manufactured in this manner is an enlarged cross-sectional view of the main part of the portion A in FIG.
As shown in (b), since the thinned portion 5a of the dielectric film 5 is covered with the second insulator film 6, in addition to the long distance between the upper electrode 7 and the lower electrode 3, By using a material having a low dielectric constant for the second insulator film 6 and reducing the voltage distribution applied to the dielectric film 5a, the withstand voltage is improved.

FIG. 3 is a diagram comparing the current-voltage characteristics of the present invention and a conventional semiconductor capacitor. The leak current flowing through the dielectric film was measured while increasing the voltage applied to the upper electrode and the lower electrode. As is clear from FIG. 3, the leak current of the conventional semiconductor capacitor is 10 ⁻⁵ A / cm ² or more at an applied voltage of 10 V, whereas the leak current of the semiconductor capacitor of the present invention is 10 ^−6.
It is A / cm ² or less, and the leak current when a voltage is applied is extremely small, and good insulation is exhibited.

In this embodiment, SrT is used as the dielectric film.
Although iO ₃ was used, it is not limited to this.
For example, SiO ₂ , Si ₃ N ₄ or the like may be used, or (B
Alternatively, a high dielectric film of a perovskite type oxide such as a, Sr) TiO ₃ or (Pb, Zr) TiO ₃ may be used. Moreover,
A mixture or a laminate of these may be used.

Further, although the example in which the lower electrode is formed directly on the silicon substrate has been described in the embodiment, the lower electrode is formed after forming an insulating film made of SiO ₂ or Si ₃ N ₄ on the silicon substrate. May be. By doing so, it is possible to insulate the conductive silicon substrate from the lower electrode. When the ground electrode is desired to be grounded, the lower electrode may be directly formed on the silicon substrate as in this embodiment.
Also, instead of the silicon substrate, GaAs, InP, Ga
It is also possible to use a compound substrate made of P.

Further, Pt will be explained as an electrode material.
But Al, Ti, Au, W, Mo, Ni, Cr, Pd
, Which is usually used in semiconductor devices as a conductive material.
There is no particular limitation as long as it is a substance
rTiO_Three, BaSrTiO _ThreePerovskite type acid
If a compound is used, it must be removed from the interface between the conductor film and the dielectric film.
Stable Pt, Au, Pd that does not form reaction products
Noble metals such as

[0019]

As described above, according to the semiconductor capacitor and the method of manufacturing the same of the present invention, since the second insulating film is formed on the side wall of the dielectric recess, it is possible to reduce the thickness of the dielectric film. An electric field is not concentrated, an increase in leak current can be suppressed, and a semiconductor capacitor having a high withstand voltage can be stably manufactured with a high yield.

[Brief description of drawings]

FIG. 1 is a sectional view showing a semiconductor capacitor of the present invention and an enlarged sectional view of essential parts.

FIG. 2 is a sectional view showing a method for manufacturing a semiconductor capacitor of the present invention.

FIG. 3 is a diagram showing current-voltage characteristics of a semiconductor capacitor of the present invention and a conventional semiconductor capacitor.

FIG. 4 is a sectional view showing a conventional method for manufacturing a semiconductor capacitor.

FIG. 5 is an enlarged sectional view of a main part of a conventional semiconductor capacitor.

[Explanation of symbols]

1 Semiconductor capacitor 2 Semiconductor substrate 3 Lower electrode 4 First insulator film 5 Dielectric film 5a Bottom of sidewall of dielectric film 6 Second insulator film 7 Upper electrode 41 Semiconductor Capacitor 42 Semiconductor substrate 43 Lower electrode 44 Interlayer insulator film 45 Dielectric film 45a Dielectric film flat portion 45b Bottom of sidewall of dielectric film 46 Upper electrode

Claims (2)

[Claims] 1. A semiconductor capacitor in which a lower electrode, a dielectric film and an upper electrode are laminated on a semiconductor substrate or an insulating film formed on the semiconductor substrate, wherein the dielectric film is recessed on the lower electrode. A semiconductor capacitor, which is formed in a rectangular shape and has an insulating film formed on a side wall of the recess of the dielectric film. 2. A step of forming a lower electrode on a semiconductor substrate or an insulating film formed on the semiconductor substrate; and a step of forming a first insulating film on the semiconductor substrate including the lower electrode, the first insulating film Forming a hole in a portion of the body film on the lower electrode, and forming the dielectric film in a concave shape on the lower electrode and the first insulator film exposed in the hole of the first insulator film. And a step of forming a second insulating film on the side wall of the concave portion of the dielectric film, the dielectric film and the second insulating film.
A method of manufacturing a semiconductor capacitor, comprising the step of forming an upper electrode on an insulating film.