KR19990055758A - Device Separating Method of Semiconductor Device - Google Patents

Abstract

The present invention relates to a method for forming a device isolation layer of a semiconductor device, wherein the polysilicon layer is formed on the sidewalls of the active region when the device isolation layer is formed, thereby reducing the step difference between the junction between the active region and the device isolation layer during the oxidation process. It is a technology that can improve the characteristics and reliability of devices by mitigating the phenomenon.

Description

Method of forming device isolation film of semiconductor device

The present invention relates to a method of forming a device isolation layer of a semiconductor device, and in particular, by forming a polysilicon layer on the sidewall of the active region when forming the device isolation layer, thereby reducing the step difference between the active region and the device isolation layer by acting as a buffer during the sacrificial oxidation process. The present invention relates to a technique for minimizing junction leakage current.

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.

As a method of manufacturing the device isolation region, a conventional local oxidation of silicon (hereinafter referred to as LOCOS) method of thermally oxidizing a semiconductor substrate using a nitride film pattern as a mask, or a trench is formed in a semiconductor substrate and embedded in an insulating material. The trench separation method is used. Among them, the LOCOS method is widely used because of its relatively simple process, but the device separation area is large and buzz is generated at the interface, so that lattice defects are generated due to stress on the substrate. have.

Looking at the manufacturing method of the LOCOS field oxide film as follows.

Hereinafter, with reference to the accompanying drawings will be described in detail.

1A to 1F are cross-sectional views illustrating a method of forming a device isolation film of a semiconductor device according to the prior art.

First, a pad insulating film 13 is formed on the semiconductor substrate 11.

Next, a first nitride layer 15 is deposited on the pad insulating layer 13.

Next, a first photosensitive film 17 is coated on the first nitride film 15.

Thereafter, an exposure and development process using an element isolation mask is performed to form the first photoresist film 17 pattern.

Subsequently, the first nitride layer 15 and the pad insulating layer 13 are patterned using the first photoresist layer 17 as an etching mask. (See FIG. 1A)

Then, the first photoresist layer 17 pattern is removed, and a second nitride layer 19 is deposited on the structure.

Next, the second nitride film 19 is subjected to an entire surface etching process to form a second nitride film spacer 19 on the sidewall of the first nitride film 15.

Thereafter, the semiconductor substrate 11 having the predetermined thickness is etched. (See FIG. 1B)

Subsequently, the exposed semiconductor substrate 11 is oxidized to form an isolation oxide layer 21. (See FIG. 1C)

Next, the spacers of the first nitride film 15 and the second nitride film 19 are removed by a wet etching process. (See FIG. 1D)

Then, the sacrificial oxide film (not shown) is formed by sacrificial oxidation of the semiconductor substrate 11 to remove the white ribbon generated by the previous process and to improve the quality of the gate oxide film formed by the subsequent process.

At this time, the active region is oxidized but does not oxidize because there is no silicon component on the device isolation region.

For the same reason, in the subsequent cleaning process of removing the sacrificial oxide film, the device isolation oxide film 21 is also etched at the same time, so that the end of the active region has a large step like the ⓐ portion. (See FIG. 1E)

Next, after the gate oxide film 23 is formed, the word line 25 is formed. (See FIG. 1F)

As described above, in the method of forming a device isolation film of a semiconductor device according to the related art, when a steep step occurs between the device isolation oxide film and the active region of the semiconductor substrate and a voltage is applied to the word line, the gate oxide film is sharp as shown in ⓑ. There is a problem in that the electric field is concentrated in the portion and leakage current occurs, and the gate oxide film is damaged and thus loses the role of the semiconductor device.

SUMMARY OF THE INVENTION The present invention provides a method for forming a device isolation film of a semiconductor device which minimizes the leakage current at the junction by reducing a step in the junction between the device isolation layer and the active region in order to solve the above problems of the prior art. have.

1A to 1F are cross-sectional views illustrating a method of forming a device isolation film of a semiconductor device according to the prior art.

2A to 2I are cross-sectional views illustrating a method of forming an isolation layer in a semiconductor device in accordance with a first embodiment of the present invention.

3A to 3F are cross-sectional views illustrating a method of forming an isolation layer in a semiconductor device in accordance with a second embodiment of the present invention.

◈ Explanation of symbols for the main parts of the drawings

11, 12, 31, 40: semiconductor substrate 13, 14: pad insulating film

15, 22, 48: first nitride film 16: polycrystalline silicon layer

17, 18, 44: first photosensitive film pattern 19, 26, 52: second nitride film

20, 46: polymer 21, 28, 54: device isolation oxide film

23: gate oxide film 24, 50: second photosensitive film pattern

25, 30: word line 42: buffer oxide film

Device isolation film forming method of a semiconductor device according to the present invention for achieving the above object,

Forming a pad insulating film and a polysilicon layer on the semiconductor substrate;

Forming a photoresist pattern on the polysilicon layer by using a device isolation mask;

Chemically treating the surface of the photoresist pattern to form a polymer;

Etching the polysilicon layer using the photoresist pattern as a mask;

Removing the photoresist pattern and forming a first nitride film over the entire surface thereof;

Etching the first nitride film by an etching process using the device isolation mask;

Forming a second nitride film spacer on the sidewall of the first nitride film;

Etching the polysilicon layer using the first nitride film and the second nitride film spacer as a mask;

Thermally oxidizing the semiconductor substrate to form an isolation layer;

It is a 1st characteristic that the process includes removing the said 1st nitride film and a 2nd nitride film spacer.

In addition, the device isolation film forming method of a semiconductor device according to the present invention for achieving the above object,

Forming a buffer insulating film on the semiconductor substrate;

Forming a photoresist pattern on the buffer insulating layer to protect a portion intended as an isolation region;

Forming a polymer on the surface of the photoresist pattern;

Removing the photoresist pattern;

Forming a first nitride film over the entire surface;

Etching the first nitride film by an etching process using the device isolation mask;

Forming a second nitride film spacer on the sidewall of the first nitride film;

Etching the polysilicon layer using the first nitride film and the second nitride film spacer as a mask;

Thermally oxidizing the semiconductor substrate to form an isolation layer;

It is a 2nd characteristic that it includes the process of removing the said 1st nitride film and a 2nd nitride film spacer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2A to 2I are cross-sectional views illustrating a method of forming an isolation layer in a semiconductor device according to a first embodiment of the present invention.

First, the pad insulating layer 14 is formed on the semiconductor substrate 12, and then the polysilicon layer 16 is formed on the pad insulating layer 14. In this case, the pad insulating layer 14 may be formed of an oxide layer, and the polysilicon layer 16 may be replaced with a material or an insulating layer that is oxidized during the oxidation process.

The first photoresist layer pattern 18 is formed on the polysilicon layer 16 to protect the device isolation region, and the first photoresist layer pattern 18 is chemically treated to form the polymer 20. In this case, the first photoresist layer pattern 18 uses a negative photoresist layer, and the reason why the polymer 20 is formed on the first photoresist layer pattern 18 is to be larger than a predetermined device isolation region. (See Figure 2A)

Next, the polysilicon layer 16 is patterned by using the first photoresist pattern 18 as an etching mask. (See Figure 2b)

Next, a first nitride film 22 is deposited on the structure, and a second photoresist pattern 24 is formed to expose a predetermined portion of the device isolation region. In this case, the second photoresist layer pattern 24 uses a positive photoresist layer. (See FIG. 2C)

The first nitride layer 22 is etched using the second photoresist layer pattern 24 as an etching mask, and then the second photoresist layer pattern 24 is removed.

Next, a second nitride film 26 is formed over the entire structure. (See FIG. 2D)

Next, the second nitride layer 26 and the polysilicon layer 16 are etched entirely to form a spacer layer of the second nitride layer 26 on the sidewalls of the first nitride layer 22 pattern. Expose (See Figure 2E)

Subsequently, the exposed semiconductor substrate 12 is oxidized to form an isolation oxide layer 28. (See Figure 2f)

In this case, the second nitride layer 26 spacer may be formed, the exposed semiconductor substrate 12 may be recessed, and an oxidation process may be performed to form the device isolation oxide layer 28.

Next, the first nitride film 16 and the second nitride film spacer 20 are removed by a wet etching process. (See Fig. 2g)

Then, the sacrificial oxide film (not shown) is formed by sacrificial oxidation of the semiconductor substrate 12 in order to remove the white ribbon generated by the previous process and to improve the quality of the gate oxide film formed by the subsequent process.

Thereafter, a washing step of removing the sacrificial oxide film is performed. Here, the device isolation oxide layer 28 is not etched because of the polysilicon layer 16 pattern formed at the boundary between the device isolation oxide 28 and the active region of the semiconductor substrate 12 during the cleaning process. Steps are prevented from occurring at the interface between the active region 28 and the semiconductor substrate 12. (See Fig. 2h)

Next, an oxide process is performed to form a gate oxide film (not shown), and a word line 30 is formed on the structure. (See Figure 2i)

3A to 3F are cross-sectional views illustrating a method of forming a device isolation film of a semiconductor device in accordance with a second embodiment of the present invention.

First, a buffer oxide layer 42 is formed on the semiconductor substrate 40, and then a first photoresist layer pattern 44 is formed on the buffer oxide layer 42 to protect the device isolation region, and the first photoresist layer pattern ( 44) is chemically treated to form polymer 46. Here, the first photoresist pattern 44 uses a negative photoresist film, and the reason why the polymer 46 is formed on the first photoresist pattern 44 is to be larger than a predetermined device isolation region. (See Figure 3a)

Next, the buffer oxide layer 44 is etched by a predetermined thickness using the first photoresist layer pattern 44 as an etching mask. (See Figure 3b)

Then, the same process as the subsequent process of Fig. 2C of the first embodiment is carried out to form an element isolation oxide film. (See Figures 3c, 3d, 3e, 3f)

As described above, the device isolation film forming method of the semiconductor device according to the present invention forms a polysilicon pattern at the boundary between the device isolation oxide film and the active region of the semiconductor substrate when the device isolation film is formed to relieve stress in the semiconductor substrate during the oxidation process. In addition, it is possible to reduce the concentration of the electric field by reducing the step at the boundary between the active region and the device isolation oxide film, thereby improving the characteristics and reliability of the semiconductor device.

Claims (5)

Forming a pad insulating film and a polysilicon layer on the semiconductor substrate; Forming a photoresist pattern on the polysilicon layer by using a device isolation mask; Chemically treating the surface of the photoresist pattern to form a polymer; Etching the polysilicon layer using the photoresist pattern as a mask; Removing the photoresist pattern and forming a first nitride film over the entire surface thereof; Etching the first nitride film by an etching process using the device isolation mask; Forming a second nitride film spacer on the sidewall of the first nitride film; Etching the polysilicon layer using the first nitride film and the second nitride film spacer as a mask; Thermally oxidizing the semiconductor substrate to form an isolation layer; And removing the first nitride film spacer and the second nitride film spacer. The method of claim 1, The etching process using the first nitride film and the second nitride film spacer, the semiconductor substrate is a device isolation film forming method of the semiconductor device, characterized in that to proceed with a recess process accompanied by a transient etching process. The method of claim 1, And the polysilicon layer is replaced with an insulating film such as an oxide film. Forming a buffer insulating film on the semiconductor substrate; Forming a photoresist pattern on the buffer insulating layer to protect a portion intended as an isolation region; Forming a polymer on the surface of the photoresist pattern; Removing the photoresist pattern; Forming a first nitride film over the entire surface; Etching the first nitride film by an etching process using the device isolation mask; Forming a second nitride film spacer on the sidewall of the first nitride film; Etching the polysilicon layer using the first nitride film and the second nitride film spacer as a mask; Thermally oxidizing the semiconductor substrate to form an isolation layer; And removing the first nitride film spacer and the second nitride film spacer. The method of claim 4, wherein The buffer insulating film etching process is a method of forming a device isolation film of a semiconductor device, characterized in that the semiconductor substrate is recessed with a transient etching process.