JPH05198744A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make films thinner without increasing leakage current and to form capacitor parts having larger capacitance values compared with those of prior art ones, by making dense the capacitor insulating films of a semiconductor device having lower and upper electrodes. CONSTITUTION:A capacitor insulating film is formed by repeating the processes of forming a silicon film 4 and nitriding the silicon film 4 thermally, at least twice or more after the formation of a lower electrode 3.

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, and more particularly to a method of forming a capacitor portion.

[0002]

2. Description of the Related Art A conventional method of forming a capacitor portion in a semiconductor device will be described with reference to FIG.

First, as shown in FIG. 3A, a lower electrode 3 is formed by a photolithography technique and an etching technique after depositing a polycrystalline silicon film by a low pressure vapor deposition method.

Next, as shown in FIG. 3 (b), rapid thermal nitriding is performed to form a thin silicon nitride film 5 on the surface of the lower electrode 3, and then a reduced pressure gas is formed as shown in FIG. 3 (c). A silicon nitride film 7 having a desired film thickness is deposited by a phase growth method.

Next, oxidation is performed in order to prevent a leak current from flowing through the silicon nitride films 5 and 7 as the capacitive insulating film, and a silicon oxide film 8 is formed as shown in FIG. 3 (d). After that, a polycrystalline silicon film is deposited by the low pressure vapor deposition method, and then the upper electrode 6 is formed by using the photolithography technique and the etching technique as shown in FIG.
Are formed to complete the capacitance section.

[0006]

By the way, as the miniaturization of the semiconductor device progresses, the occupied area of the capacitor portion becomes smaller, and it becomes increasingly difficult to secure the capacitance value. For this reason, increasing the surface area of the capacitor electrode and thinning the capacitor insulating film have been studied as means for securing the capacitance value.

At present, the thinning of the capacitance insulating film is 5n.
However, since the silicon nitride film as the capacitive insulating film deposited by the low pressure vapor deposition method is a sparse film, the leakage current flowing through the capacitive insulating film becomes abrupt when the thickness is further reduced. However, there is a problem in that it does not play the role of the capacitance section.

Further, if the thickness is further reduced, the oxidation resistance of the silicon nitride film is deteriorated due to the oxidation process after the deposition of the silicon nitride film by the low pressure vapor phase epitaxy method, and the oxide film is formed thick. There is a problem that the capacity value required for the device cannot be obtained.

The present invention has been proposed in view of the above problems of the prior art, and in a semiconductor device having a lower electrode, a capacitive insulating film, and an upper electrode, by making the capacitive insulating film a dense film, leakage occurs. It is an object of the present invention to provide a method for manufacturing a semiconductor device, which is capable of forming a thin film without increasing the current and forming a capacitor portion having a larger capacitance value than a conventional one.

[0010]

According to the method of manufacturing a semiconductor device of the present invention, a capacitor insulating film is formed by repeating a step of forming a silicon film and a step of thermally nitriding the silicon film after forming a lower electrode. It is characterized by doing.

According to the present invention, a groove portion having a predetermined size is formed on the semiconductor substrate, and a lower electrode is formed so as to cover the groove,
The step of forming a silicon film after the formation of the lower electrode and the step of thermally nitriding the silicon film are repeated at least twice to form a capacitive insulating film and to fill the groove for forming the capacitive insulating film. A method for manufacturing a semiconductor device is obtained which is characterized in that

[0012]

The present invention will be described below with reference to the drawings.

FIG. 1 is a process flow diagram for forming a capacitor portion of a semiconductor device showing a first embodiment of the present invention.

First, a polycrystalline silicon film is deposited on the semiconductor substrate 1 in which the openings are formed in the silicon oxide film 2 by the low pressure vapor deposition method. After that, the lower electrode 3 is formed by the photolithography technique and the etching technique (FIG. 1A). The method of forming the lower electrode 3 is the same as the conventional method.

Next, after depositing a polycrystalline silicon film 4 to a thickness of 1 nm by a reduced pressure vapor deposition method using SiH4 gas at a temperature of 600 ° C. (FIG. 1 (b)), a lamp annealing apparatus is used. The polycrystalline silicon film 4 is nitrided by annealing in a NH ₃ atmosphere at 850 ° C. for 60 seconds to
A 5 nm silicon nitride film 5 is formed (FIG. 1C).

Next, after the second-layer polycrystalline silicon film 4 is deposited by the low pressure vapor deposition method under the same conditions as the case of depositing the first-layer polycrystalline silicon film 4 (FIG. 1 (d)). The second-layer silicon nitride film 5 is formed under the same conditions as when the first-layer silicon nitride film 5 was formed by the lamp annealing apparatus (FIG. 1E). In this state, a silicon nitride film with a total thickness of 3 nm is formed.

Next, after depositing a polycrystalline silicon film having a desired film thickness by the low pressure vapor deposition method, the upper electrode 6 is formed by the photolithography technique and the etching technique to complete the capacitor portion (FIG. 1 (f). )).

Silicon nitride film 5 formed by this method
Is denser than the silicon nitride film formed by the conventional low pressure vapor phase epitaxy method and does not have pinholes. Therefore, it is possible to eliminate the oxidation step which was conventionally performed to eliminate the pinholes in the silicon nitride film. You can

Further, according to the method of the present invention, since the oxidation step is not necessary, a thick silicon oxide film is formed due to the oxidation resistance blur even if the silicon nitride film is thin, which is necessary for a semiconductor device. The conventional problem that the capacitance value cannot be obtained does not occur.

The lower limit film thickness at which the silicon nitride film formed by the conventional method can function as a capacitive insulating film is about 5 nm due to the problem of leak current.
Since the silicon nitride film is a dense film according to the present invention, there is no problem that the leak current increases even if the film thickness is reduced to about 3 nm.

Therefore, by reducing the film thickness of the silicon nitride film to three-fifths of the conventional lower limit film thickness, the capacitance value can be increased to three-fifths of the conventional value.

FIG. 2 is a process flow chart for forming a capacitor portion of a semiconductor device showing a second embodiment of the present invention.

First, as shown in FIG. 2A, after forming a groove by a photolithography technique and an etching technique, impurities are implanted to form a lower electrode 3. Then the first
In the same manner as in Example 1, the step of depositing a polycrystalline silicon film by the low pressure vapor phase epitaxy method and the step of rapid thermal nitriding the film by a lamp annealing device are repeated to form a silicon nitride film 5 having a thickness of 3 nm (FIG. 2 (b)).

Next, a polycrystalline silicon film having a desired film thickness is deposited by the reduced pressure vapor deposition method, and then the upper electrode 6 is formed by the photolithography technique and the etching technique to complete the capacitor portion (see FIG. 2 ( c)). Also in the second embodiment, the silicon nitride film is densely formed and can be made thinner than the conventional lower limit film thickness. Therefore, the second embodiment has the same effect as that of the first embodiment, and by using the second embodiment, it becomes easy to flatten the element.

[0025]

As described above, according to the present invention, by repeating the step of forming a silicon film after forming the lower electrode and the step of thermally nitriding the silicon film, the silicon nitride deposited by the low pressure vapor phase epitaxy method is repeated. Since a film denser than the film can be formed, the oxidation step after forming the silicon nitride film is unnecessary. In addition, there is an effect that the capacitance insulating film can be thinned and the capacitance value can be increased to 5 times the conventional value without increasing the leak current.

As a result, as shown in FIG. 4, there is an effect that the hold failure rate, which was about 3 to 20% in the past, can be reduced to 5% or less.

[Brief description of drawings]

FIG. 1 is a process flow diagram of forming a capacitor portion of a semiconductor device showing a first embodiment of the present invention.

FIG. 2 is a process flow chart of forming a capacitor portion of a semiconductor device showing a second embodiment of the present invention.

FIG. 3 is a process flow diagram of a conventional semiconductor device capacitor section.

FIG. 4 is a correlation between a manufacturing method and a hold failure rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2 ... Silicon oxide film 3 ... Lower electrode 4 ... Polycrystalline silicon film 5 ... Silicon nitride film 6 ... Upper electrode 7 ... Silicon nitride film 8 ... Silicon oxide film

Claims (2)

[Claims] 1. A semiconductor device having a lower electrode, a capacitive insulating film and an upper electrode, wherein the step of forming a silicon film after the formation of the lower electrode and the step of thermally nitriding the silicon film are repeated at least twice. A method of manufacturing a semiconductor device, comprising forming a capacitive insulating film. 2. A groove portion having a predetermined size is formed on a semiconductor substrate,
A lower electrode is formed so as to cover the groove, and a step of forming a silicon film after forming the lower electrode and a step of thermally nitriding the silicon film are repeated at least twice to form a capacitor insulating film, and A method of manufacturing a semiconductor device, comprising forming an upper electrode so as to fill a groove for forming a capacitance insulating film.