JPH0555361A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a semiconductor device provided with a trench as an element isolating region, where a substrate on which elements are formed is lessened in stress and level difference by a method wherein the change of processes which can be easily carried out is executed. CONSTITUTION:A semiconductor device is provided with a trench 1a as an element isolating region, a silicon thermal oxide film 3, a silicon nitride film 4, and a silicon oxide film 5 are successively inside the trench 1a, and a polysilicon film 6 whose surface is covered with a thermal oxide film 6a is formed so as to film the center part of the trench 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a trench as an element isolation region and a method of manufacturing the same.

In order to cope with the miniaturization of semiconductor devices in recent years due to higher integration, it is necessary to make the area used as an element isolation region as small as possible, and to prevent a decrease in product yield. Are required to reduce the stress of the substrate on which the device is formed and to reduce the steps formed.

Under the circumstances as described above, a semiconductor device having an element isolation region capable of reducing stress on a substrate on which an element is formed and reducing a step formed in an area as small as possible, and a method of manufacturing the same are provided. Is requested.

[0004]

2. Description of the Related Art A conventional semiconductor device using a trench as an element isolation region and a method of manufacturing the same will be described in detail with reference to FIGS.

FIG. 5 is a side sectional view showing a trench portion of a conventional semiconductor device, and FIGS. 6 to 8 are side sectional views showing a method of manufacturing the conventional semiconductor device in the order of steps. As shown in FIG. 5, a conventional semiconductor device using a conventional trench as an element isolation region has a silicon thermal oxide film 13 and a silicon nitride film 14 sequentially stacked in a trench 11a formed in a semiconductor substrate 11. The polysilicon film 16 which is formed and whose surface is covered with the thermal oxide film 16a is formed so as to fill the central portion of the trench 11a.

A method of manufacturing such a semiconductor device will be described with reference to FIGS.
Details will be described in order of steps with reference to FIG. First, as shown in FIG. 6A, a resist is applied to the surface of the semiconductor substrate 11 to form a resist film 12, and the resist film is patterned by a photolithography technique using a mask to form an opening 12a in the trench 11a forming portion. Then, a trench 11a with a width of 1.0 μm and a depth of 5.0 μm is formed in the semiconductor substrate 11 by dry etching, and then ion is implanted by ion implantation using the resist film 12 as a mask to form a channel cut 11b in the trench 11a. Formed on the bottom of the.

Next, the resist film 12 is removed to remove the semiconductor substrate.
When 11 is heated to 1,000 ° C to form a silicon thermal oxide film extending on the surface of the semiconductor substrate 11 and the sidewalls and bottom of the trench 11a, the sidewall of the trench 11a has a film thickness of 3,000 as shown in Fig. 6 (b). Å Silicon thermal oxide film 13 becomes trench 11a
Is about 7,000Å.

Then, as shown in FIG. 7A, a silicon nitride film 14 having a film thickness of 500 Å is formed on the entire surface of the silicon thermal oxide film 13 by C.
When formed by the VD method, the width of the trench 11a is about 6,000.
Become Å.

Further, as shown in FIG. 7B, the semiconductor substrate 11
A polysilicon film 16 having a thickness of 2 μm is formed on the surface of the silicon nitride film 14 and the surface of the silicon nitride film 14 extending to the side wall and the bottom surface of the trench.
When grown by the VD method, the central portion of the trench is filled with the polysilicon film 16.

When the entire surface of the polysilicon film 16 is etched by dry etching, the polysilicon film 16 remains in the trench and the silicon nitride film 14 is exposed on the surface of the semiconductor substrate 11 as shown in FIG. 8 (a). To do.

When the semiconductor substrate 11 is heated to 900 to 1,000 ° C., the surface of the polysilicon film 16 is thermally oxidized to form a thermal oxide film 16a as shown in FIG. 8 (b). The film thickness at the boundary is formed thinner than that at the center.

Finally, when dry etching is performed, the silicon nitride film 14 having a film thickness of about 500 Å on the surface is removed, and as shown in FIG. 5, the thermal oxide film 16a at the boundary of the trench 11a has a film thickness at the center. It is thinner than the thickness.

[0013]

In the semiconductor device manufactured by the manufacturing method described above, as shown in FIG. 5, the polysilicon film 16 filled in the trench 11a is thermally oxidized to form a silicon thermal oxide film on the surface. In the case of 16a, the film thickness of the thermal oxide film 16a formed in the portion in contact with the silicon nitride film 14 is smaller than that in the central portion due to insufficient oxygen supply, so the film in this portion is formed. If the thickness is made necessary, the thickness of the central portion becomes unnecessarily thick, the stress of the semiconductor substrate 1 becomes large, and the step between the thermal oxide film 16a and the silicon thermal oxide film 13 becomes large. was there.

In view of the above situation, the present invention can reduce the stress on the substrate on which the element is formed and the steps formed by changing the process that can be easily performed. And a method for manufacturing the same.

[0015]

The semiconductor device of the present invention comprises:
A semiconductor device having a trench as an element isolation region, in which a silicon thermal oxide film, a silicon nitride film, and a silicon oxide film are sequentially stacked in a trench formed in a semiconductor substrate, and the surface is A polysilicon film covered with a thermal oxide film is configured to fill the center of this trench.

A method of manufacturing a semiconductor device according to the present invention is the method of manufacturing a semiconductor device described above, wherein a channel cut is formed in a bottom portion, a sidewall and a bottom surface of a trench formed in the semiconductor substrate, and the semiconductor substrate. A step of forming a silicon thermal oxide film extending on the surface and sequentially forming a silicon nitride film and a silicon oxide film on the entire surface of this silicon thermal oxide film, and a step of forming a silicon nitride film and a silicon oxide film on the center part of this trench and the surface of this silicon oxide film. A step of forming an existing polysilicon film, a step of completely etching the polysilicon film to expose the surface of the silicon oxide film, and a step of thermally oxidizing the surface of the polysilicon film to form a thermal oxide film. And a step of removing the silicon oxide film and the silicon nitride film on the surface of the semiconductor substrate.

[0017]

That is, in the present invention, after the silicon oxide film is formed on the entire surface of the silicon nitride film formed in the trench,
Since the polysilicon film is filled and the polysilicon film is thermally oxidized to form a thermal oxide film, the oxide film at the boundary portion of the trench 1a becomes thicker than the central portion in this oxidation step. Since it suffices to form a thermal oxide film having a desired thickness, it is possible to reduce the thickness of the entire thermal oxide film, reduce the stress on the semiconductor substrate that forms the element, and reduce the steps formed. It becomes possible to

[0018]

1 to 4, a semiconductor device using a trench as an element isolation region and a method of manufacturing the same according to an embodiment of the present invention will be described in detail below.

FIG. 1 is a side sectional view showing a trench portion of a semiconductor device according to one embodiment of the present invention, and FIGS. 2 to 4 are side sectional views showing a method of manufacturing a semiconductor device according to one embodiment of the present invention in the order of steps. is there.

A semiconductor device using a trench as an element isolation region according to one embodiment of the present invention has a silicon thermal oxide film 3 and a silicon nitride film in a trench 1a formed in a semiconductor substrate 1 as shown in FIG. A film 4 and a silicon oxide film 5 are sequentially laminated and formed, and a polysilicon film 6 whose surface is covered with a thermal oxide film 6a is filled in the central portion of the trench 1a.

A method of manufacturing such a semiconductor device will be described with reference to FIGS.
Detailed description will be given in order of steps with reference to FIG. First, as shown in FIG. 2A, a resist film 2 is formed by applying a resist on the surface of the semiconductor substrate 1, and the resist film is patterned by a photolithography technique using a mask to form an opening 2a in the trench 1a forming portion. Then, a trench 1a having a width of 1.0 μm and a depth of 5.0 μm is formed in this semiconductor substrate 1 by dry etching, and then ion is implanted by the ion implantation method under the following conditions using the resist film 2 as a mask to form a channel cut 1b. Are formed at the bottom of the trench 1a.

Ion species ────── Boron (B ⁺ ), implantation energy ─
────── 20 keV Dose ────── 5 × 10 ¹² cm ^-2 Next, the resist film 2 is removed, and the semiconductor substrate 1 is heated to 1,000 °.
When the silicon thermal oxide film is formed on the surface of the semiconductor substrate 1 and the sidewalls and bottom surface of the trench 1a by heating to C, as shown in FIG.
As shown in (b), the side wall of the trench 1a becomes the silicon thermal oxide film 3 having a film thickness of 3,000Å, and the width of the trench 1a becomes about 7,000Å.

Then, as shown in FIG. 3 (a), a silicon nitride film 4 having a film thickness of 500 Å is formed on the entire surface of the silicon thermal oxide film 3 by C.
When the silicon oxide film 5 having a film thickness of 500 Å is formed on the entire surface of the silicon nitride film 4 by the CVD method by the VD method, the width of the trench 1a becomes about 5,000 Å.

Further, as shown in FIG. 3 (b), the semiconductor substrate 1
A polysilicon film 6 having a film thickness of 2 μm is formed on the surface of the silicon nitride film 4 and the surface of the silicon nitride film 4 extending to the side wall and the bottom surface of the trench.
When grown by the VD method, the central part of the trench is filled with the polysilicon film 6.

When the entire surface of the polysilicon film 6 is etched by dry etching, the polysilicon film 6 remains in the trench and the silicon oxide film 5 is exposed on the surface of the semiconductor substrate 1 as shown in FIG. 4 (a). To do.

When the semiconductor substrate 1 is heated to 900 to 1,000 ° C., the surface of the polysilicon film 6 is thermally oxidized to form a thermal oxide film 6a of about 4,000 liters as shown in FIG. 4 (b). When dry etching is performed at the end, the surface film thickness is about 5
The silicon oxide film 5 of 00 Å and the silicon nitride film 4 under it having a film thickness of about 500 Å are removed, and the trench 1a as shown in FIG. 1 is removed.
It is possible to manufacture a semiconductor device including the thermal oxide film 6a having a thick oxide film at the boundary portion of the.

In the above embodiment, the silicon thermal oxide film 3 and the trench 1a on the surface of the semiconductor substrate 1 are processed in the step of FIG. 2 (b).
Although the silicon thermal oxide film 3 on the inner wall is formed at the same time, it is also possible to previously form the silicon thermal oxide film on the surface of the semiconductor substrate 1 and then form the silicon thermal oxide film 3 in the trench 1a. Is.

[0028]

As is apparent from the above description, according to the present invention, it is possible to reduce the stress on the substrate on which the element is formed and to reduce the step difference formed by the extremely simple structure change. It is possible to provide a semiconductor device and a method for manufacturing the same, which have advantages such as the above, and can be expected to achieve significant economic and reliability improvement effects.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a trench portion of a semiconductor device according to an embodiment of the present invention,

FIG. 2 is a sectional side view (1) showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps,

FIG. 3 is a side sectional view (2) showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps;

FIG. 4 is a side sectional view (3) showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps;

FIG. 5 is a side sectional view showing a trench portion of a conventional semiconductor device,

FIG. 6 is a side sectional view (1) showing a conventional semiconductor device manufacturing method in the order of steps;

FIG. 7 is a side sectional view (2) showing a conventional method of manufacturing a semiconductor device in the order of steps.

FIG. 8 is a sectional side view (3) showing a conventional method of manufacturing a semiconductor device in the order of steps,

[Explanation of symbols]

1 is a semiconductor substrate, 1a is a trench, 1b
Is a channel cut, 2 is a resist film, 2a is an opening, 3 is a silicon thermal oxide film, 4 is a silicon nitride film, 5 is a silicon oxide film, 6 is a polysilicon film, 6a is a thermal oxide film,

Claims (2)

[Claims] 1. A semiconductor device having a trench (1a) as an element isolation region, wherein the trench (1a) formed in a semiconductor substrate (1) comprises:
A silicon thermal oxide film (3), a silicon nitride film (4), and a silicon oxide film (5) are sequentially stacked, and the surface is a thermal oxide film.
A semiconductor device characterized in that a polysilicon film (6) covered with (6a) is formed so as to fill the central portion of the trench (1a). 2. The method of manufacturing a semiconductor device according to claim 1, wherein a channel cut (1b) is formed on a bottom portion, and a sidewall and a bottom surface of a trench (1a) formed on the semiconductor substrate (1), Silicon thermal oxide film extending on the surface of the semiconductor substrate (1)
(3) and then sequentially forming a silicon nitride film (4) and a silicon oxide film (5) on the entire surface of the silicon thermal oxide film (3), the center portion of the trench (1a) and the silicon. Oxide film (5)
A step of forming a polysilicon film (6) extending on the surface of the silicon oxide film, a step of completely etching the polysilicon film (6) to expose the surface of the silicon oxide film (5), and the polysilicon film (6). The surface of (6) is thermally oxidized to form a thermal oxide film (6
a), and a step of removing the silicon oxide film (5) and the silicon nitride film (4) on the surface of the semiconductor substrate (1). ..