JP2000058775A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device which can prevent the generation of insulation separation caused by voids in a buried electrode in a trench. SOLUTION: In a trench formed in a silicon substrate 2, a first amorphous silicon film 26 is formed and then a silicon oxide film is formed on the first amorphous silicon film 26. After forming the silicon oxide film, the first amorphous silicon film 26 is heat-treated to be crystallized. Thereafter, the silicon oxide film is removed and then a second amorphous silicon film 30 is formed on the first amorphous silicon film 26 to fill the trench.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device for filling a trench formed in a semiconductor substrate, and more particularly to a method of forming a trench capacitor formed in a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, phosphorus (P) has been used as a method of forming an electrode in a trench (hereinafter referred to as a trench) dug in a silicon substrate.
Alternatively, there is a method in which an amorphous silicon film to which arsenic (As) is added is buried in the trench. Since the amorphous silicon film has fewer seams and voids than the polycrystalline silicon film, the trench can be filled with a relatively uniform film.

[0003] Regarding the conventional trench filling method,
A bottle-shaped trench, which is one of the trench shapes, that is, a trench having a so-called 'Botlle Shape Trench' structure will be described with reference to FIG. Figure 8 shows the 'Botlle Shape Tre
FIG. 9 is a diagram showing a cross-sectional structure when an nch ′ structure trench is buried with an amorphous silicon film.

As shown in FIG. 8A, a silicon nitride film 102 and a silicon oxide film 104 are formed on a side surface and a bottom surface of a trench formed in a silicon semiconductor substrate (hereinafter referred to as a silicon substrate) 100. I have. In such a semiconductor substrate, an amorphous silicon film 106 to which phosphorus (P) or arsenic (Ag) is added is buried by LPCVD in the whole inside of the trench.

On the surface of the silicon substrate 100, a silicon oxide film 108 is formed, and further, a silicon nitride film 110 and a silicon oxide film 112 used as a mask when forming the trench are formed.

[0006]

However, according to the above-described conventional trench filling method,
When the trench of the “Botlle Shape Trench” structure is buried with the amorphous silicon film 106, a large void 114 may be formed at the center of the trench as shown in FIG. This large void 114
FIG. 8
As shown in (b), the amorphous silicon film 1 serving as an electrode
06 may be completely separated at the top and bottom.

When the electrodes are separated as described above, the area of the capacitor is reduced, and the intended capacitance of the capacitor cannot be obtained. The present invention has been made in view of the above problems, and has as its object to provide a method of manufacturing a semiconductor device capable of preventing insulation separation due to voids or the like in a buried electrode of a trench.

[0008]

In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention comprises the steps of: forming a first silicon film in a trench formed in a semiconductor substrate; A step of performing a heat treatment on the first silicon film to increase a density of the first silicon film; and a step of forming a second silicon film on the first silicon film. .

In a method of manufacturing a semiconductor device according to the present invention, a first silicon film is formed in a trench formed in a semiconductor substrate, and an insulating film is formed on the first silicon film. And after forming the insulating film, the first
Crystallizing the first silicon film by performing a heat treatment on the first silicon film, and removing the insulating film and forming a second silicon film on the first silicon film. It is characterized by.

In a method of manufacturing a semiconductor device according to the present invention, a step of forming a first silicon film serving as an electrode in a trench formed in a semiconductor substrate, and a step of forming an insulating film on the first silicon film Forming the insulating film and, after forming the insulating film, performing a heat treatment on the first silicon film to crystallize the first silicon film to increase the density of the first silicon film; Removing the insulating film and removing the first
Forming a second silicon film to be an electrode on the silicon film, and forming an electrode made of the first silicon film and the second silicon film in the trench. .

Further, in the method of manufacturing a semiconductor device according to the present invention, the total thickness of the first silicon film and the insulating film is smaller than half the diameter of the narrowest portion of the trench. I do.

Further, the method of manufacturing a semiconductor device according to the present invention is characterized in that the first silicon film and the second silicon film are amorphous silicon films. Also,
The method of manufacturing a semiconductor device according to the present invention further comprises the first method.
Heat treatment after the formation of the silicon film and the insulating film
It is performed at a temperature of 00 ° C. or higher.

Further, in the method of manufacturing a semiconductor device according to the present invention, the insulating film on the first silicon film is a silicon oxide film. Further, in the method for manufacturing a semiconductor device according to the present invention, the insulating film on the first silicon film is a silicon nitride film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.
Here, as the trench shape, in order to increase the surface of the trench, a bottle-shaped trench having a larger diameter inside the trench, that is, a trench having a so-called 'Botlle Shape Trench' structure will be described.

FIGS. 1 to 7 are cross-sectional views of respective manufacturing steps showing a method of manufacturing a semiconductor device according to this embodiment. First,
A method for forming a trench having a 'Botlle Shape Trench' structure will be described. As shown in FIG. 1A, a silicon oxide film (SiO ₂ film) 4 is formed on a silicon semiconductor substrate (hereinafter, silicon substrate) 2 by performing thermal oxidation in a high-temperature oxidizing atmosphere. Further, the CVD is performed on the silicon oxide film 4.
A silicon nitride film 6 and a silicon oxide film 8 are sequentially formed by a method.

Subsequently, as shown in FIG. 1B, a 'Bottom' is formed on the silicon oxide film 8 by photolithography.
A resist pattern 10 having an opening at the neck of the le Shape Trench 'structure is formed, and the silicon oxide film 8, silicon nitride film 6, and silicon oxide film 4 on the trench formation region are removed. Thereafter, the resist pattern 10 is removed by a plasma ashing method or the like.

Next, using the silicon nitride film 6 and the silicon oxide film 8 as masks, as shown in FIG.
The trenches 12 are formed by etching the silicon substrate 2 by an IE (Reactive Ion Etching; RIE) method. In the present embodiment, as described above, the trench 1
'Botlle Shape' which further processed No. 2 and increased the diameter inside the trench to increase the surface area of the trench
Create a trench with a Trench 'structure.

The trench having the 'Botlle Shape Trench' structure is formed by the following method. FIG.
As shown in (b), a silicon nitride film 14 is formed on the inner wall of the trench 12 and on the silicon oxide film 8. continue,
As shown in FIG. 3A, the inside of the trench 12 in which the silicon nitride film 14 has been formed is filled with a photoresist film 16.

Thereafter, as shown in FIG.
The photoresist film 16 is etched to a predetermined depth by a (Chemical Dry Etching) method to form a photoresist film 16a. Further, using this photoresist film 16a as a mask, as shown in FIG.
The silicon nitride film 14 is etched to the predetermined depth to form a silicon nitride film 14a. Then, the photoresist film 16a is completely removed.

Next, the silicon substrate 2 having the structure shown in FIG. 4A is oxidized in a steam atmosphere at a temperature of 800 ° C. to 1100 ° C., thereby forming the trench 12 as shown in FIG. Thermal oxide film 18 is formed only on the upper side wall of. Thereafter, as shown in FIG.
The silicon nitride film 14a in 2 is removed. Further, FIG.
As shown in FIG. 2B, the lower sidewall of the trench 12 where the thermal oxide film 18 is not formed is etched by CDE to form a bottle-shaped trench 20. Thus, the trench 20 having the 'Botlle Shape Trench' structure is completed.

Next, a method for forming an electrode in the trench 20 will be described. As shown in FIG. 6A, a silicon nitride film 22 is formed in the trench 20 of the silicon substrate 2 by LPCVD. Subsequently, a very thin silicon oxide film 24 is formed on the surface of the silicon nitride film 22 by thermally oxidizing the surface of the silicon nitride film 22.

Further, phosphorus (P) or arsenic (Ag) is formed on the ultra-thin silicon oxide film 24 by LPCVD.
Is added to form a first amorphous silicon film 26. At this time, in the LPCVD method, SiH ₄ , PH ₃ , or AsH ₃ is used as a gas source and the temperature is 520 ° C. to 60 ° C.
The film is formed under the conditions of 0 ° C. and a pressure of 0.2 Torr to 1.0 Torr. If the amorphous silicon film is used, a uniform film can be formed at a low temperature under a relatively low temperature condition.

Subsequently, as shown in FIG. 6A, a silicon oxide film (Si) is formed on the first amorphous silicon film 26.
An O ₂ film 28 is formed. This silicon oxide film 28
The film is formed by TEOS or LPCVD using SiH ₄ and N ₂ O as a gas source.

The silicon oxide film 28 is not limited to this, but may be a silicon nitride film. At this time, the total thickness of the first amorphous silicon film 26, the silicon oxide film 28, and the silicon nitride film 22 is made smaller than half the diameter of the neck portion, which is the narrowest portion of the trench 20. This is to prevent the trench 20 from being closed by the stacked film of the first amorphous silicon film 26, the silicon oxide film 28, and the silicon nitride film 22.

Next, by subjecting the trench 20 to a heat treatment at a temperature of 600 ° C. or higher, the first amorphous silicon film 26 is completely crystallized as shown in FIG. Thereby, the first amorphous silicon film 26 is formed.
Density increases. As described above, by increasing the density of the first amorphous silicon film 26, the first amorphous silicon film 26 is deformed by a heat treatment at a temperature of 1000 ° C. or more in a subsequent manufacturing process. The occurrence of insulation separation of the electrode made of the amorphous silicon film 26 or the like is prevented. At this time, by forming the silicon oxide film 28 on the first amorphous silicon film 26, it is possible to prevent the first amorphous silicon film 26 from aggregating.

Thereafter, as shown in FIG. 7, the silicon oxide film 28 is removed by wet etching using an NH ₄ F solution or the like, and then a second CVD method is formed on the first amorphous silicon film 26 by LPCVD. Of amorphous silicon 30 is deposited. Thus, the second amorphous silicon 3
The trench 20 is buried with an electrode composed of the first amorphous silicon film 26 and the first amorphous silicon film 26. Thus, the formation of the electrodes in the trench 20 is completed.

As described above, in this embodiment, the first silicon film and the insulating film are formed in the trench, and the thickness of the first silicon film and the thickness of the insulating film are combined. Is thinner than half the diameter of the narrowest part of the trench. Then, by performing a heat treatment at a temperature of 600 ° C. or higher, the first silicon film is crystallized and the density of the first silicon film is increased. At this time, by providing an insulating film on the first silicon film,
Aggregation of the first silicon film is suppressed.
After that, the insulating film is removed, and a second silicon film is formed to fill the trench with the electrodes made of the first and second silicon films.

As described above, in this embodiment, a silicon film to be an electrode in a trench is formed in two steps, and a heat treatment is performed at a temperature of 600 ° C. or more after the first silicon film is formed. It is possible to prevent the silicon film from being deformed due to the heat treatment in the manufacturing process of (1) and the electrodes in the trenches being electrically separated (insulated). Even if a void is formed in the trench after the second silicon film is formed, the first silicon film has a high density, so that no insulating separation occurs in the electrode.

[0029]

As described above, according to the present invention, it is possible to provide a method of manufacturing a semiconductor device capable of preventing insulation separation due to voids or the like in a buried electrode of a trench.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of each manufacturing step showing a method for manufacturing a semiconductor device of this embodiment.

FIG. 2 is a cross-sectional view of each manufacturing step showing the method for manufacturing a semiconductor device of this embodiment.

FIG. 3 is a cross-sectional view of each manufacturing step showing the method for manufacturing a semiconductor device of the embodiment.

FIG. 4 is a cross-sectional view of each manufacturing step showing the method for manufacturing a semiconductor device of this embodiment.

FIG. 5 is a cross-sectional view of each manufacturing step showing the method for manufacturing a semiconductor device of this embodiment.

FIG. 6 is a cross-sectional view of each manufacturing step showing the method for manufacturing a semiconductor device of this embodiment.

FIG. 7 is a cross-sectional view of each manufacturing step showing the method for manufacturing a semiconductor device of the embodiment.

FIG. 8 is a diagram for explaining a problem caused by a conventional trench filling method.

[Explanation of symbols]

2: Silicon semiconductor substrate 4: Silicon oxide film (SiO ₂ film) 6: Silicon nitride film 8: Silicon oxide film 10: Resist pattern 12: Trench 14, 14a: Silicon nitride film 16, 16a: Photoresist film 18: Thermal oxidation Film 20 trench 22 silicon nitride film 24 silicon oxide film 26 first amorphous silicon film 28 silicon oxide film 30 second amorphous silicon film

Claims (8)

[Claims] In a trench formed in a semiconductor substrate,
Forming a first silicon film, performing a heat treatment on the first silicon film to increase the density of the first silicon film, and forming a second silicon film on the first silicon film. Forming a semiconductor device. 2. In a trench formed in a semiconductor substrate,
Forming a first silicon film; forming an insulating film on the first silicon film; performing heat treatment on the first silicon film after forming the insulating film; A method of manufacturing a semiconductor device, comprising: crystallizing a silicon film; and forming a second silicon film on the first silicon film by removing the insulating film. 3. A semiconductor device comprising: a trench formed in a semiconductor substrate;
Forming a first silicon film to be an electrode; forming an insulating film on the first silicon film; performing heat treatment on the first silicon film after forming the insulating film. Crystallizing the first silicon film to increase the density of the first silicon film; removing the insulating film to form a second silicon film serving as an electrode on the first silicon film; Forming an electrode made of the first silicon film and the second silicon film in the trench. 4. The method according to claim 1, wherein the total thickness of the first silicon film and the insulating film is smaller than half the diameter of the thinnest portion of the trench. The manufacturing method of the semiconductor device described in the above. 5. The method for manufacturing a semiconductor device according to claim 1, wherein said first silicon film and said second silicon film are amorphous silicon films. 6. The semiconductor device according to claim 1, wherein the heat treatment after forming the first silicon film and the insulating film is performed at a temperature of 600 ° C. or higher. Production method. 7. The method of manufacturing a semiconductor device according to claim 1, wherein said insulating film on said first silicon film is a silicon oxide film. 8. The method of manufacturing a semiconductor device according to claim 1, wherein said insulating film on said first silicon film is a silicon nitride film.