JPH04326568A - Capacity element - Google Patents

Abstract

PURPOSE:To enable a dielectric film to be thinned so as to enlarge the capacity per unit area, in an MIM-type capacity element being made in an IC. CONSTITUTION:A dielectric film 5 is made on the section of the lower electrode 3a consisting of the high melting point metallic film 3 (Ti, W, Mo, TiN, WSi, and MoSi) at the first layer on the field insulating film 2 on a semiconductor substrate 1, and wiring film 4 is made on other part, and an upper electrode 6 consisting of high melting point metal at the second layer is made on the above dielectric film 5. An Al film 7 made on the topside of the upper electrode 6 prevents the upper electrode 6 from being corroded by the selective etching to a layer insulating film 8. Contact holes 9 and 10 are made in the layer insulating film 8, and Al films 11 and 12 for taking out the upper and lower electrodes are made. Even if it is heat-treated, hyrocs or voids do not occur in the electrode consisting of high melting point metal, so the dielectric film can be thinned, and the capacity per unit area can be made large.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive element, and particularly to a capacitive element formed within an IC.

0002

[Prior Art] A normal capacitive element formed in an IC is
It had an MIS structure as shown in FIG. 9(A). In the drawing, a is a p-type semiconductor substrate, b is an n-type epitaxial layer, c is a p+-type isolation layer, and d is an n+-type diffusion layer formed on the surface of the epitaxial layer, which connects the lower electrode of the capacitive element. I will do it. e is a dielectric film formed in the opening g of the insulating film f, and is made of, for example, LPSiN (low pressure CVD).
It is made of SiN) or SiO2, and is in direct contact with the diffusion layer d.

Reference character h is an electrode film made of aluminum formed in another opening g of the insulating film f, and i is an upper electrode made of aluminum formed on the dielectric film e. In such a capacitive element having an MIS structure, the lower electrode of the capacitive element is formed by a highly doped diffusion layer d in order to reduce parasitic resistance, but it is unavoidable that a parasitic resistance r of about 10 -2 Ωcm is generated. In addition, the pn junction between the p-type semiconductor substrate a and the n-type epitaxial layer b provides 1×10−
It is also unavoidable that a parasitic capacitance Ca of 8 F/cm2 occurs. FIG. 9B shows an equivalent circuit of the MIS type capacitive element. If the parasitic resistance and capacitance are large as described above, it is difficult to improve the frequency characteristics.

[0004] Therefore, a capacitive element having an MIM structure as shown in FIG. 10 was developed as a high frequency capacitive element. This capacitive element has a lower electrode k made of aluminum formed on a field insulating film f of a semiconductor substrate a, and an upper electrode m made of aluminum formed on the lower electrode k via a dielectric film l.
was formed. n is a terminal electrode of the lower electrode k. Such a capacitive element has a parasitic resistance of 3 x 10-9F.
/cm2, and the parasitic capacitance is 3 x 10-6Ω, which is extremely small compared to MIS type capacitive elements.
It can be said that it is excellent in that respect.

[0005]

[Problem to be solved by the invention] However, MIM
This type of capacitive element uses aluminum or aluminum-based metal for the lower and upper electrodes, so heat treatment after forming the lower and upper electrodes can cause hillocks and voids that can break the dielectric film. , there was a risk that a short circuit would occur between the lower electrode k and the upper electrode m. Therefore, in order to avoid this, it was necessary to increase the thickness of the dielectric film l. Specifically, the film thickness needed to be 4000 angstroms or more. However, if the thickness of the dielectric film is increased in this way, the capacitance per unit area of the capacitive element becomes smaller, and as a result, the area occupied by the dielectric film becomes larger. This is IC, LSI, VLSI
This is undesirable because it becomes a factor that hinders high integration.

The present invention has been made to solve these problems, and an object of the present invention is to increase the capacitance per unit area of a capacitive element.

[0007]

[Means for Solving the Problems] The capacitive element of the present invention has a first
A dielectric film is formed on a portion of the high-melting point metal film that will become the lower electrode, a wiring film is formed on the other portion, and a second upper layer of the high-melting point metal film is formed on the dielectric film. It is characterized by forming an electrode.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the capacitive element of the present invention will be explained in detail according to the illustrated embodiments. FIGS. 1(A) and 1(B) show one embodiment of the capacitive element of the present invention, where (A) is a cross-sectional view and (B) is a cross-sectional view.
FIG. 3 is a plan view showing the lower electrode. In the drawings, 1 is a semiconductor substrate, 2 is a field insulating film, and 3 is a first layer high-melting point metal film, such as titanium Ti, titanium nitride TiN, tungsten W, molybdenum Mo, tungsten silicide WSi, or molybdenum silicide Mo.
Consists of Si. 3a is a lower electrode portion of the high melting point metal film 3, and 3b is a wiring film portion of the high melting point metal film 3.

Reference numeral 4 denotes a wiring film made of aluminum formed on the wiring film portion of the first layer high melting point metal film 3, and is formed on the wiring film portion 3b of the high melting point metal film 3. 5 is a dielectric film formed to completely cover the lower electrode 3a, for example, plasma nitride P-SiN, plasma silicon monoxide P-SiO, silicon dioxide SiO2.
, PSG, etc. The dielectric film 5 is made as thin as, for example, about 1000 angstroms. 6 is a dielectric film 5
An upper electrode made of a second layer of high-melting point metal formed above is opposed to the lower electrode 3a with the dielectric film 5 in between, and the opposing electrodes 3a, 6 and the dielectric film therebetween. 5 forms a capacitive part which is the main part (principal part) of this capacitive element.

7 is an aluminum film (or silicon-containing aluminum film) formed on the upper surface of the upper electrode 6;
The selective etching of the interlayer insulating film 8 described below serves to prevent the high melting point metal 6 forming the upper electrode from being corroded. In other words, it serves as an etching stopper. 9 and 10 are contact holes formed in the interlayer insulating film 8, and 11 and 12 are aluminum films for taking out the upper and lower electrodes.

According to the present capacitive element, since the counter electrodes 3a and 6, which are the main parts and face each other with the dielectric film 5 in between, are made of a high melting point metal, hillocks and voids are generated by heat treatment after forming the counter electrodes. There is no danger. Therefore, even if the dielectric film 5 is made considerably thinner than the conventional one, there is no risk of a short circuit occurring between the opposing electrodes 3a and 6. Therefore, the capacitance per unit occupied area of the capacitor can be increased, and the capacitor can be downsized. Specifically, the area occupied by the capacitive part, which is the main part of the capacitive element, can be reduced to about one-fourth that of a conventional MIM type capacitive element.

FIGS. 2 to 8 are cross-sectional views showing an example of a method for manufacturing the capacitive element shown in FIG. 1 in the order of steps. (1) A first layer of high melting point metal film 3 is formed on the surface of field insulating film 2 on silicon semiconductor substrate 1, and a first layer of aluminum wiring film 4 is formed on the high melting point metal film 3. . The wiring film 4 and the high melting point metal film 3 are formed by sputtering. FIG. 2 shows the state after the wiring film 4 and the high melting point metal film 3 are formed.

(2) Next, as shown in FIG.
Then, the high melting point metal film 3 is patterned by wet etching. This patterning is performed so that only the lower electrode of the capacitor portion and the wiring portion connected to the lower electrode remain. (3) Next, as shown in FIG.
The layered aluminum film 4 is etched except for the portion located above the portion where the lower electrode is to be formed. 3a shows the lower electrode exposed by this etching of the first layer high melting point metal film 3, and 3b shows the part under the first layer aluminum film 4.

(4) Next, as shown in FIG. 5, a dielectric film 5 is formed by, for example, CVD. (5) Next, as shown in FIG. 6, a second layer of high melting point metal film 6 and a second layer of aluminum film 7 are formed. (6) Next, as shown in FIG. 7, the second layer high melting point metal film 6 and the second layer aluminum film 7 are patterned. As a result, the upper electrode 6 is formed from the second layer of high melting point metal. (7) Next, as shown in FIG. 8, an interlayer insulating film 8 is formed.

Thereafter, contact holes 9 and 10 are formed by selectively etching the interlayer insulating film 8, and then an aluminum film is formed by sputtering, and then wiring films 11 and 12 are formed by patterning the aluminum film. form. As mentioned above, during the selective etching of the interlayer insulating film 8, the aluminum film 7 plays a role as a protective film (so-called etching stopper) to prevent etching of the upper electrode 6 made of a thin high-melting point metal. be.

[0016]

Effects of the Invention In the capacitive element of the present invention, a dielectric film is formed on a part of the first layer of the high melting point metal film that will become the lower electrode, and a wiring film is formed on the other part of the high melting point metal film. A second layer of an upper electrode made of a high melting point metal is formed on the dielectric film. Therefore, according to the capacitive element of the present invention, since the counter electrode is formed of a high melting point metal instead of an aluminum film as in the conventional case, there is a risk that hillocks or voids may be generated in the counter electrode due to heat treatment after forming the counter electrode. There is no. Therefore, even if the dielectric film is thin, short circuit accidents between opposing electrodes will not occur. Therefore,
The dielectric film can be made thinner, and the electrostatic capacitance per unit occupied area of the capacitive element can be increased, and the capacitive element can be made smaller.

[Brief explanation of drawings]

[Fig. 1] (A) and (B) show one embodiment of the capacitive element of the present invention, in which (A) is a cross-sectional view, and (B) is a plane showing a lower electrode and a wiring film connected thereto. It is a diagram.

FIG. 2 is a cross-sectional view showing a first step of an example of a method for manufacturing the capacitive element shown in FIG. 1;

FIG. 3 is a cross-sectional view showing the second step.

FIG. 4 is a cross-sectional view showing the third step.

FIG. 5 is a cross-sectional view showing the fourth step.

FIG. 6 is a cross-sectional view showing the fifth step.

FIG. 7 is a cross-sectional view showing the sixth step.

FIG. 8 is a cross-sectional view showing the seventh step.

[Fig. 9] (A) and (B) show one conventional example;
(A) is a cross-sectional view, and (B) is an equivalent circuit diagram.

FIG. 10 is a sectional view showing another conventional example.

[Explanation of symbols]

3. First layer high melting point metal film 3a Lower electrode 3b Wiring film 4 Wiring film 5 Dielectric film

Claims (1)

[Claims] 1. A dielectric film is formed on a part of the first layer high melting point metal film that will become the lower electrode, a wiring film is formed on the other part of the high melting point metal film, and the dielectric film is formed on the other part of the high melting point metal film. A capacitive element characterized in that a second layer of an upper electrode made of a high melting point metal is formed on a film.