JPH06151707A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device manufacturing method with which a semiconductor device can be manufactured easily by electrically connecting it to other circuit elements completely while a large capacitor is being manufactured without being affected by stray capacity and the like, and the capacitor, to be electrically connected to other IC-constituting elements, is formed on the insulating film which is insulated from a circuit element. CONSTITUTION:A capacitor part is formed by successively laminating a lower electrode film, a silicon nitride film and an upper electrode film on the insulating film provided on the surface of a semiconductor substrate and by conducting a patterning operation thereon. The lower electrode is exposed by providing a contact hole 2a on the electrode terminal forming part of the lower electrode. A recessed part 2b is formed by etching a silicon nitride film 6 which is exposed to the side face of the contact hole 2a, the end parts 2c of the contact hole 2a are smoothed by reflowing by conducting a heat treatment, the oxide film on the lower electrode 3, which is oxidized by heat treatment, is removed by etching, and an electrode terminal 9 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device. More specifically, it relates to a method for manufacturing a semiconductor device having a capacitor connected to another circuit element as a circuit element of an integrated circuit device (hereinafter referred to as an IC).

[0002]

2. Description of the Related Art As shown in FIG. 5, a capacitor connected to a transistor or the like as a circuit element of an IC is an oxide serving as a dielectric on a silicon substrate 51 which is a semiconductor substrate on which the connected transistor or the like is provided. A film 52 is provided, a polysilicon layer 53 serving as an upper electrode doped with impurities is provided thereon, and a metal layer 54 serving as an upper electrode terminal is provided above the polysilicon layer 53.

In a capacitor having this structure, one electrode portion is composed of a metal layer 54 and a polysilicon layer 53, and the other electrode is, for example, a silicon substrate 51 on which a collector of a transistor is formed. Connected with. The oxide film 52 is usually used as a dielectric material interposed between both electrodes of this capacitor in connection with other steps. Since the dielectric constant of the oxide film 52 is small, it is necessary to widen the area of the electrode or reduce the film thickness of the oxide film 52 in order to increase the capacitance. However, if the area of the electrode is widened, the capacitor element becomes large and the integration degree of the IC cannot be improved. Also, if the thickness of the oxide film 52 is reduced, the withstand voltage performance of the capacitor is reduced and discharge becomes easier, and at the same time,
At the manufacturing stage of IC, pinholes are easily generated in this oxide film, which lowers the reliability of IC, and the limit is about 30Å.

Further, since this capacitor uses the silicon substrate 51 as one of the electrodes, the stray capacitance tends to increase.
That is, there is a drawback in that an accurate capacitance cannot be obtained because of being easily influenced by other circuit elements on the silicon substrate 51.

[0005]

As described above, since the conventional capacitor uses the silicon substrate 51 as one of the electrodes, it is easily affected by electrical effects from other circuit elements, and the accurate capacitance as designed cannot be obtained. I can't. Further, since the silicon oxide film is used as the dielectric between the electrodes, there is a problem that the capacitance of the capacitor cannot be increased without increasing the surface area.

On the other hand, the capacitor is not directly provided on the surface of the semiconductor substrate on which the circuit element connected to the capacitor is formed, but the lower electrode, the silicon nitride film, or the like is formed at a place unrelated to the semiconductor circuit element such as a field insulating film. It may be possible to form a capacitor by laminating a dielectric film having a large dielectric constant and an upper electrode, but in the case of forming an electrode terminal connected to the lower electrode in order to connect the lower electrode to another circuit element, , The following problems occur. That is, after forming the contact hole, reflow is performed to improve the coverage (heat treatment is performed to smooth the corner portion of the contact hole), and then the oxide film formed on the lower electrode is removed to remove the fluorine. Although an etching treatment is performed with an acid or the like, these treatment liquids usually etch the silicon oxide film, but it is difficult to etch the silicon nitride film. Therefore, there is a problem in that the silicon nitride film has a protruding portion and the connection between the electrode wiring and the lower electrode becomes insufficient.

The present invention has been made in order to solve such a problem, has no stray capacitance, and can improve the degree of integration even if the capacitance value is increased. An object of the present invention is to provide a method for manufacturing a semiconductor device having a capacitor that does not hinder the operation.

[0008]

A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having a capacitor in which an integrated circuit is formed on a semiconductor substrate and connected to other circuit elements in the circuit. A lower electrode, a silicon nitride film, and an upper electrode are sequentially laminated on an insulating film provided on a substrate surface and patterned to form the capacitor portion, and the electrode terminal of the lower electrode is (a) the lower electrode. Etching the silicon nitride film and the protective film provided on the lower electrode in the electrode terminal forming part to form a contact hole, and (b) etching the silicon nitride film exposed on the side surface of the contact hole. After forming a recess and smoothing the corners of the contact hole by (c) heat treatment, the oxide film formed on the lower electrode film by the heat treatment is removed by etching. (D) is characterized by the formation by providing the electrode terminals become the metal film in the contact hole.

[0009]

According to the method of manufacturing a semiconductor device of the present invention, a capacitor connected to another circuit element is formed by laminating a lower electrode, a silicon nitride film and an upper electrode on an insulating film of a semiconductor substrate. , It is possible to obtain a capacitor having stable capacitance as designed without being electrically affected by other elements on the substrate, and adopting silicon nitride having a large dielectric constant as the dielectric film of the capacitor. Can
The capacitance of the capacitor can be increased without increasing the surface area of the electrodes. Furthermore, after the contact hole of the connection wiring of the lower electrode is provided, the exposed portion of the silicon nitride film is etched and then heat-treated, and then the oxide film is removed. It is possible to obtain a highly reliable semiconductor device which is formed without fear, allows reliable connection between elements.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing the capacitor of the present invention will be described below with reference to the drawings.

FIG. 1 shows I prepared by the manufacturing method of the present invention.
2 is a cross-sectional view showing an example of the capacitor portion of C, FIG. 2 is a process diagram showing a step of forming the capacitor part in FIG. 1 in the manufacturing method which is one embodiment of the manufacturing method of the present invention, and FIG. 3 is a manufacturing method of the present invention. 1 is a process diagram showing a step of forming a terminal portion of a lower electrode in a manufacturing method which is one embodiment, and FIG. 4 is a sectional view showing an essential part of another example of an IC capacitor manufactured by the manufacturing method of the present invention. Is.

First, an example of a capacitor manufactured by the manufacturing method of the present invention will be described.

In FIG. 1, 1 is a capacitor part,
Reference numeral 2 is a terminal portion for a lower electrode (hereinafter referred to as a polysilicon layer) 3 formed of the polysilicon layer of the capacitor portion 1.

The capacitor portion 1 and the terminal portion 2 are both formed on a silicon substrate 4 which is a semiconductor substrate with a field oxide film 5 interposed therebetween. Therefore, both the capacitor section 1 and the terminal section 2 are not electrically affected by other elements on the same substrate, and the capacitance value as planned can be obtained accurately.

Since the silicon nitride film 6 having a large dielectric constant is used as the dielectric in the capacitor section 1, a large capacitance value can be obtained. Next, a method of manufacturing the capacitor section will be described.

As shown in FIG. 2A, a lower electrode of a capacitor is provided by using a polysilicon film or silicide on an insulating film made of, for example, silicon oxide or silicon nitride provided on a semiconductor substrate. As a specific example, a field oxide film 5 made of silicon dioxide is formed on one surface of a silicon substrate 4 by a thermal oxidation method or the like, and a polysilicon layer 3 serving as a lower electrode is formed on the upper surface of the field oxide film 5. Then, a phosphine (P
Impurities were diffused under an atmosphere such as H ₃ ). Then, the polysilicon layer 3 is masked and etched to form a lower electrode having a desired pattern of the capacitor in consideration of the terminal portion.

Next, as shown in FIG. 2B, a dielectric film made of silicon nitride is laminated on the lower electrode. As a specific example, a Si ₃ N ₄ film 6 forming a dielectric film was laminated on the entire surface of the substrate 4 by the CVD method.

Then, as shown in FIGS. 2 (c) and 2 (d), a protective film made of, for example, a silicon oxide film or an SOG film is laminated on the entire surface by, for example, a CVD method or a coating method to form an upper electrode for forming a capacitor. Is provided by etching with, for example, hydrofluoric acid, and an upper electrode made of, for example, Al—Si, polysilicon, or the like is provided. Since this protective film has an opening,
It is necessary to selectively etch the silicon nitride film, which is a dielectric film, and the silicon nitride film and the silicon nitride film are laminated with a material having different etching characteristics. As a specific example, a SiO ₂ film 7 as a protective film is formed on the upper surface of the Si ₃ N ₄ film 6 by a CVD method. After that, as shown in FIG. 2D, the upper surface of the SiO ₂ film 7 is patterned and etched for the upper electrode to form an opening, and the Si ₃ N ₄ film 6 exposed at the bottom of the opening 6 is formed. Then, a metal film 8 made of aluminum or the like, which constitutes the upper electrode terminal, was formed by sputtering.

The capacitor portion 1 is formed by the above steps. Next, a method of forming the terminal portion 2 for the lower electrode will be described.

The lower electrode terminal portion 2 is the capacitor portion 1
This is for providing a connection wiring for connecting the lower electrode to another circuit element at another place. The lower electrode terminal portion 2 is formed at a different location from the capacitor portion 1, but the lower electrode is laminated at the same time as the formation of the capacitor portion 1,
It is formed by exposing the lower electrode at the laminated portion of the silicon nitride film and the protective film. First, as shown in FIG. 3E, a reactive ion etching method (hereinafter referred to as RIE method)
The protective film 7 and the silicon nitride film 6 are etched by, for example, to form the contact hole 2a, and the lower electrode 3 is exposed. As a specific example, the SiO ₂ film 7 and the Si ₃ N ₄ film 6 were removed by etching in a predetermined pattern by the RIE method to form the contact hole 2a for the terminal portion 2.

Next, the silicon nitride film 6 is etched with an etching solution such as hot phosphoric acid for etching the silicon nitride film 6 to form a recess 2b as shown in FIG. 3 (f). As a specific example, the substrate 4 was immersed in hot phosphoric acid at about 100 to 150 ° C. for 40 to 80 minutes for treatment. At this time, the polysilicon layer 3 and the SiO ₂ film 7 are not easily dissolved by hot phosphoric acid. Therefore, the contact hole 2a
Only the Si ₃ N ₄ film 6 exposed on the inner surface of the was slightly dissolved, and a recess 2b was formed as shown in FIG. 3 (f).

Next, in order to prevent disconnection of the electrode film, heat treatment is performed to smooth the edge portion 2c of the contact hole 2a and reflow is performed (see FIG. 3 (g)). Subsequently, in order to remove the oxide film formed on the lower electrode 3 by heat treatment, the oxide film is etched with, for example, hydrofluoric acid (see FIG. 3H). At this time, the silicon nitride film 6 is hard to be etched by the etching liquid, and only the silicon nitride film 6 is etched in the previous step to form the recess 2b, so that no protrusion is formed. As a specific example, the substrate 4 is 900
Reflow was carried out by holding at ~ 950 ° C for about 30 minutes. By doing so, the corner portion 2c of the SiO ₂ contact hole 2a was melted and smoothed as shown in FIG. Subsequently, treatment with hydrofluoric acid was performed for 0.5 to 2 minutes. As a result, even when the polysilicon layer 3 is exposed at the bottom of the contact hole 2a, the smooth periphery and bottom of the contact hole 2a are maintained, and the metal film for the electrode terminal 9 shown in FIG. When it is formed, problems such as disconnection were prevented.

Then, aluminum, Al--Si, Al
A metal film of —Si—Cu or the like is provided by a vapor deposition method, a sputtering method, or the like, and is etched to provide an electrode terminal 9 for connection wiring, which is connected to another circuit element. As a specific example, an aluminum film having a thickness of 7,000 to 10,000 Å was formed by a vapor deposition method and patterned by dry etching to provide an upper electrode.

As described above, the lower electrode 3 terminal portion 2 of the IC capacitor is connected to other circuit elements, and the IC capacitor shown in FIG. 1 is completed in the integrated circuit device.

FIG. 4 shows a capacitor portion 11 formed by a forming method according to another embodiment of the present invention. This capacitor unit 11 is the same as that in the above-described embodiment (see FIGS. 1 and 2).
(See (d)) is different in that the second polysilicon layer 12 is formed on the upper surface of the silicon nitride film 6 and the metal film 10 for terminals is formed. With this structure, the area of the second polysilicon layer 12 can be set by etching,
It is possible to easily and accurately obtain the capacitance value as designed.

[0026]

According to the manufacturing method of the present invention, the stray capacitance does not affect the capacitor, the capacitance value as designed can be obtained, and the area of the capacitor does not increase, so that the degree of integration can be improved. Further, the connection wiring of the lower electrode of the capacitor can be formed with high reliability, and a semiconductor device having a high quality IC capacitor can be obtained.

[Brief description of drawings]

FIG. 1 is an I prepared by an embodiment of the manufacturing method of the present invention.
It is a section explanatory view showing an example of a capacitor part for C.

FIG. 2 is a process drawing showing a step of forming a capacitor portion in the manufacturing method which is an embodiment of the manufacturing method of the present invention.

FIG. 3 is a process drawing showing a step of forming a terminal portion of a lower electrode in the manufacturing method which is an embodiment of the manufacturing method of the present invention.

FIG. 4 is an explanatory cross-sectional view of essential parts showing an example of an IC capacitor part manufactured by another embodiment of the manufacturing method of the present invention.

FIG. 5 is a cross-sectional view showing an example of a conventional IC capacitor.

[Explanation of symbols]

 1 Capacitor Part 2 Terminal Part 2a Contact Hole 3 Lower Electrode (Polysilicon Layer) 4 Silicon Substrate 5 Field Oxide Film 6 Silicon Nitride Film 8 Upper Electrode 9 Electrode Terminal

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device having a capacitor, in which an integrated circuit is formed on a semiconductor substrate and connected to other circuit elements in the circuit, the method comprising: forming an insulating film on a surface of the semiconductor substrate. The lower electrode, the silicon nitride film and the upper electrode are sequentially laminated and patterned to form the capacitor portion, and the electrode terminal of the lower electrode is formed on the lower electrode in the electrode terminal forming portion of the lower electrode (a). The silicon nitride film and the protective film provided on the substrate are etched to form contact holes, (b) the silicon nitride film exposed on the side surfaces of the contact holes is etched to form recesses, and (c) heat treatment is performed. After smoothing the corners of the contact hole by etching, the oxide film formed on the lower electrode film by the heat treatment is removed by etching. A method of manufacturing a semiconductor device, which is formed by providing a metal film to be an electrode terminal.