KR19990003058A - Device Separation Method of Semiconductor Device - Google Patents

Abstract

The present invention relates to a method for manufacturing a device isolation film of a semiconductor device, by performing a conventional PBL process twice to form a device isolation film to eliminate the step difference between the active region and the field region to ensure the margin of the subsequent process to improve the reliability of the device It is about a technique to improve.

According to the present invention, a first pad oxide film, a first polycrystalline silicon film, and a first nitride film are sequentially formed on a semiconductor substrate, and then a first nitride film pattern is formed using a first device isolation mask. After thermally oxidizing a predetermined portion of the substrate to form a first device isolation oxide film, the first nitride film and the first polycrystalline silicon film are removed, the first device isolation oxide film is removed by a wet process, and then a PBL process is performed again. A device isolation film manufacturing method of a semiconductor device forming a second device isolation oxide film is provided.

Description

Device Separation Method of Semiconductor Device

The present invention relates to a method for manufacturing a device isolation film of a semiconductor device, and in particular, by performing a conventional poly buffered locos (PBL) process twice to form a device isolation film, the step difference between the active region and the field region is eliminated to reduce the margin of the subsequent process. It relates to a technique for securing and improving the reliability of the device.

In general, a semiconductor device is composed of an active region in which devices such as a transistor or a capacitor are formed, and an isolation region separating the active regions so that the operation of the devices does not interfere with each other.

Recently, with the trend toward higher integration of semiconductor devices, efforts have been made to reduce the area of device isolation regions, which occupy a large area in semiconductor devices.

Such a device isolation region manufacturing method includes a conventional LOCOS method for thermally oxidizing a silicon semiconductor substrate using a nitride film pattern as a mask, or a SEFOX method for thermally oxidizing a separate polysilicon layer laminated on a semiconductor substrate. Trench isolation is used to form trenches in semiconductor substrates and fill them with insulating materials.

Among them, the LOCOS method is widely used because of its relatively simple process, but has a large device isolation area, and generates a buzz big at the interface, thereby causing lattice defects due to substrate stress.

Although not shown in the drawings, a method of manufacturing a semiconductor device according to the prior art will be described.

First, the surface of the semiconductor substrate is thermally oxidized to form a pad oxide film having a relatively thin thickness, and a polycrystalline silicon film having a predetermined thickness is formed on the pad oxide film.

Next, a nitride film pattern serving as a thermal oxidation mask is formed on the polycrystalline silicon film, and the predetermined thickness of the exposed semiconductor substrate is removed by an anisotropic etching method.

Then, thermal oxidation is performed to form a device isolation oxide film, and the thermal oxidation mask and the polysilicon film are removed.

According to the conventional technology as described above, the PBL method used for device isolation between the active region and the field region has a step difference between the active region and the field region in a process specific manner, and thus, an attack occurs during pattern formation of a subsequent process. It will have a bad effect.

In addition, it is possible to cause a problem of securing and refreshing the active area by Buzz Big, which is a problem that becomes more serious as the device area is reduced.

Accordingly, the present invention is to solve the above problems, but to perform the conventional PBL process twice, first to remove the step between the active region and the field region by performing a primary PBL process to form a device isolation oxide film, secondary It is an object of the present invention to provide a device isolation film manufacturing method of a semiconductor device which improves the reliability of the device by securing a margin of a subsequent process by forming a device isolation oxide film under the semiconductor substrate by performing a PBL process.

1A to 1F are process drawings of device isolation films of a semiconductor device according to the present invention.

* Explanation of symbols for the main parts of the drawings

20: semiconductor substrate, 22,30: first and second pad oxide films, 24,32: first and second polycrystalline silicon films, 26,34: first and second nitride films, 28,36: first and second device isolation oxide films

In order to achieve the above object, a device isolation film manufacturing method of a semiconductor device according to the present invention

Sequentially forming a first pad oxide film, a first polycrystalline silicon film, and a first nitride film on the semiconductor substrate;

Etching the first nitride film, the first polycrystalline silicon film, and the first pad oxide film using a first device isolation mask to form a first nitride film pattern;

Thermally oxidizing the exposed semiconductor substrate to form a first device isolation oxide film;

Removing the first nitride film and the first polycrystalline silicon film by an etching process;

Removing the first device isolation oxide film by a wet process;

Sequentially forming a second pad oxide film, a second polysilicon film, and a second nitride film on the entire surface of the structure;

Forming a second nitride film pattern using a second device isolation mask;

Thermally oxidizing the exposed semiconductor substrate to form a second device isolation oxide film;

And removing the second nitride film and the second polysilicon film by an etching process.

Hereinafter, a device isolation film manufacturing method of a semiconductor device according to the present invention will be described in detail with reference to the accompanying drawings.

1A to 1F are diagrams illustrating a process of fabricating an isolation layer of a semiconductor device according to the present invention.

First, the first pad oxide film 22, the first polysilicon film 24, and the first nitride film 26 are sequentially formed on the semiconductor substrate 20.

Here, the first polysilicon film 24 serves to alleviate the nitride film stress in a subsequent process, and the first nitride film 26 is selectively oxidized when the device isolation film is grown in a subsequent process for device isolation between active regions. It acts as a mask for.

Next, the first nitride layer 26 is etched using the first device isolation mask until the semiconductor substrate 20 is exposed (see FIG. 1A).

Then, the exposed semiconductor substrate 20 is thermally oxidized to form a first isolation oxide layer 28 (see FIG. 1B).

Next, the first nitride film 26 and the first polysilicon film 24 are removed by an etching process, and then the first device isolation oxide film 28 is removed by a wet process.

At this time, the stepped portions of the active region and the field region are removed through the PBL process (see FIG. 1C).

Then, the second pad oxide film 30, the second polysilicon film 32, and the second nitride film 34 are sequentially formed on the entire surface of the structure.

Next, the second nitride film 34 pattern is formed using the second device isolation mask.

Here, the second device isolation mask is used as the same as the first device isolation mask.

Then, the exposed semiconductor substrate 20 is thermally oxidized to form a second isolation oxide layer 36 (see FIG. 1D).

Next, the second isolation layer 34 and the second polysilicon layer 32 are removed by an etching process to form an isolation layer to secure a margin of a subsequent process (see FIG. 1E).

As described above, according to the present invention, the element isolation film is formed by performing the PBL process twice in forming the device isolation film, thereby preventing attack in the device region, thereby enhancing device isolation characteristics between the active regions, By improving the step difference between the field and the field area to secure a margin during the subsequent process has the advantage of improving the reliability of the device.

Claims (2)

Sequentially forming a first pad oxide film, a first polycrystalline silicon film, and a first nitride film on the semiconductor substrate; Etching the first nitride film, the first polycrystalline silicon film, and the first pad oxide film using a first device isolation mask to form a first nitride film pattern; Thermally oxidizing the exposed semiconductor substrate to form a first device isolation oxide film; Removing the first nitride film and the first polycrystalline silicon film by an etching process; Removing the first device isolation oxide film by a wet process; Sequentially forming a second pad oxide film, a second polysilicon film, and a second nitride film on the entire surface of the structure; Forming a second nitride film pattern using a second device isolation mask; Thermally oxidizing the exposed semiconductor substrate to form a second device isolation oxide film; And removing the second nitride film and the second polysilicon film by an etching process. The method of claim 1, wherein the first and second device isolation masks use the same mask.