KR20070026985A - Method of isolating elements in a semiconductor device - Google Patents

Abstract

A method for isolating a semiconductor device is provided to improve a gap-fill capability of a trench without the generation of voids or seams and to prevent active pitting by forming a densified helium oxide layer using a heat treatment process on a substrate and supplying hydrogen source gas. A heat treatment process is performed on a substrate(100) with an isolation trench in a temperature range of 400 deg.C or more. A helium oxide layer(108) is continuously formed along an inner surface of the isolation trench by performing a first high density plasma treatment on the resultant structure using a first reaction gas containing helium. A hydrogen oxide layer is filled in the isolation trench by performing a second high density plasma treatment on the resultant structure using a second reaction gas containing H2.

Description

Method of isolating elements in a semiconductor device

1 is a photograph showing a defect generated when performing a high density plasma process.

2 is a graph for explaining a temperature change of a substrate according to a high density plasma process condition.

3 is a cross-sectional view illustrating a pad oxide film pattern and a hard mask pattern formed on a substrate.

4 is a cross-sectional view illustrating a trench formed by the hard mask pattern illustrated in FIG. 3.

FIG. 5 is a cross-sectional view for describing a heat treatment process of the trench illustrated in FIG. 4.

FIG. 6 is a cross-sectional view illustrating a helium oxide film formed on the trench illustrated in FIG. 5.

FIG. 7 is a cross-sectional view illustrating a silicon oxide film formed in a trench in which a helium oxide film shown in FIG. 6 is formed.

FIG. 8 is a cross-sectional view illustrating a silicon oxide film pattern formed from the silicon oxide film shown in FIG. 7.

Explanation of symbols on the main parts of the drawings

100 semiconductor substrate 102 pad oxide film pattern

104: hard mask pattern 106: trench

108: helium oxide film 110: silicon oxide film

112: silicon oxide pattern

The present invention relates to a device isolation method of a semiconductor device. More particularly, the present invention relates to a method of separating an element by forming an isolation layer in a trench formed in a semiconductor substrate.

In recent years, with the rapid spread of information media such as computers, semiconductor devices are also rapidly developing. In terms of its function, the semiconductor device is required to operate at a high speed and to have a large storage capacity. In response to such demands, manufacturing techniques have been developed for semiconductor devices to improve the degree of integration, reliability, and response speed. As a technology for improving the degree of integration of the semiconductor device, a processing technology for forming a region for electrically separating the elements constituting the semiconductor device has been important. The area electrically separating the devices should occupy a narrow area and be effectively insulated. The process of forming the device isolation is an initial step in all semiconductor manufacturing process steps, and depends on the size of the active region and the process margin of subsequent processes.

The processing technology includes a LOCOS (LoCal Oxidation of Silicon) technology or a trench (Shallow Trench Isolation (STI) technology). Recently, a trench technology that occupies a small area and secures an insulation margin by depth is mainly used.

A method of forming a device isolation region using the trench technique may be described in brief. A pad oxide layer and a hard mask pattern may be sequentially formed on a semiconductor substrate, and the pad oxide layer and the semiconductor substrate may be etched using the hard mask pattern as an etching mask. Form.

Subsequently, the trench is filled with an insulating film for element isolation. The insulating film for device isolation is a silicon oxide film and is usually formed by a high density plasma (HDP) process.

Silicon nitride (SiN ₄ ) source gas and oxygen (O ₂ ) as the reaction gas of the deposition process A mixed gas containing a source gas is used to form a silicon oxide film (SiO ₂ ) in the trench. In addition, helium (He) is used as a plasma atmosphere forming gas for forming the plasma.

However, as the semiconductor devices are highly integrated, the sizes of the active regions and the field regions are greatly reduced, and accordingly, the widths of the trenches for forming the field regions are very narrow and their depths are relatively deep.

As described above, as the aspect ratio of the trench is increased, it is very difficult to fill the oxide film without the occurrence of voids or seams in the trench.

In addition, since the deposition rate of the oxide film at the edge of the trench is faster than the deposition rate at the bottom or sidewall of the trench, voids or deep light may be generated in the trench.

Therefore, there is a need for a method of performing the high density plasma process and minimizing damage caused by the plasma. Therefore, the RF power is reduced, or a liner that is not damaged by plasma in advance, that is, a free coating layer is introduced in advance. In the case of the above method, the damage caused by the above-described plasma can be reduced, but the ability to fill the gap is inferior.

To prevent these voids and seams from occurring, hydrogen with excellent gap-fill capability Use gas as source gas. The hydrogen gas has a very small particle size, good straightness, and excellent gap filling properties. However, an active pitting phenomenon frequently occurs in which the active region is locally filled when the hydrogen gas fills the trench by performing the high density plasma process.

1 is a photograph showing a defect generated when performing a high density plasma process.

Referring to FIG. 1, part A is an active fitting phenomenon generated after filling the trench by performing a high density plasma process using the hydrogen gas as a reaction gas. The active phenomenon occurs when hydrogen gas used as a reaction gas diffuses into the active in the high density plasma process.

The unit device formed in the region where the active fitting is generated may have an operation failure or poor operation characteristics. Therefore, the occurrence of the active fitting adversely affects the yield of the semiconductor device and the reliability of the semiconductor device.

An object of the present invention for solving the above problems is to prevent the occurrence of the active fitting, and to provide a device separation method of the semiconductor device without the occurrence of voids or seams.

According to an aspect of the present invention for achieving the above object, a high-density plasma process using a reaction gas containing a helium gas for heating the substrate on which the trench for device isolation is formed to a temperature of 400 ℃ or more Performing a high density plasma process using a reactive gas containing hydrogen gas on the helium oxide film to continuously form a helium oxide film on the bottom and side surfaces of the trench; .

In this case, the helium oxide film is formed to a thickness of 300 kPa to 400 kPa. The trench may sequentially deposit a pad oxide layer and a hard mask layer on a substrate, and pattern the hard mask layer and the pad oxide layer to form a hard mask pattern and a pad oxide layer pattern, and convert the hard mask pattern into an etch mask. It is formed by performing the step of etching the substrate.

According to the present invention as described above, before filling the trench formed on the substrate with the oxide film, the substrate is heated, and then a high density plasma process is performed to form a densified helium oxide film in the trench, thereby proceeding hydrogen The diffusion of hydrogen is prevented during the high density plasma process using the gas as a reaction gas.

The high density plasma process is typically performed at high vacuum and high power compared to atmospheric pressure chemical vapor deposition (AP-CVD), low pressure chemical vapor deposition (LP-CVD) or plasma enhanced chemical vapor deposition (PE-CVD). Therefore, when the film is formed by the HDP-CVD process, the film structure is dense and the mechanical properties of the film are excellent. Here, the mechanical property refers to a property that can obtain reproducible results when performing unit processes such as etching and polishing.

Subsequently, by performing a high-density plasma process using a gas containing hydrogen to form a silicon oxide film having good gap filling characteristics, diffusion of hydrogen can be prevented and the gap filling characteristics can be improved. According to this method, by forming the helium oxide film before filling the trench, hydrogen diffusion is prevented in a subsequent high density plasma process. Then, by filling the trench by performing a high density plasma process using hydrogen gas as a reaction gas, it is possible to prevent the occurrence of an active fitting phenomenon and to minimize the generation of voids or seams.

Hereinafter, a device isolation method of a semiconductor device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments and may be implemented in other forms. The embodiments introduced herein are provided to make the disclosure more complete and to fully convey the spirit and features of the invention to those skilled in the art. In the drawings, the thickness of each device or film (layer) and regions has been exaggerated for clarity of the invention, and each device may have a variety of additional devices not described herein. If (layer) is mentioned as being located on another film (layer) or substrate, it may be formed directly on another film (layer) or substrate, or an additional film (layer) may be interposed therebetween.

Table 1 is a table showing whether the active fitting is generated according to the substrate temperature when the helium oxide film is formed on the heated substrate.

Process conditions Substrate temperature (℃) Active fitting occurs Plasma Power (W) Time (s) 3000 30 300 ο 3000 40 350 ο 3000 120 400 × 4250 120 500 ×

According to the result of Table 1, as the plasma power and time are changed, the substrate temperature also changes. In this case, the active fitting occurs when the helium oxide film is deposited at a temperature of 350 ° C. or lower, and the active fitting does not occur when the helium oxide film is deposited at a temperature of 400 ° C. or higher.

Accordingly, after the densified helium oxide film is formed at a temperature of 400 ° C. or higher, a high density plasma process may be performed using the hydrogen as a reaction gas to prevent the occurrence of active fitting.

2 is a graph for explaining a temperature change of a substrate according to a high density plasma process condition.

Referring to FIG. 2, the portion A is plasma power of 3000 W, the formation time of the helium oxide film when the substrate is heated for about 40 seconds, the portion B of plasma power is 4250 W, and the substrate is heated to about 120 seconds. It is the formation time of a helium oxide film.

At this time, the formation time of the helium oxide film is A and B takes a short time of 3 to 4 seconds. Therefore, it can be seen that the formation of the helium oxide film is greatly influenced by the temperature of the substrate. As the temperature of the substrate is increased, the temperature at which the helium oxide film is formed increases, and a densified helium oxide film is formed. The densified helium oxide film may prevent active fitting from occurring by preventing the hydrogen from diffusing when a subsequent high density plasma process is performed using subsequent hydrogen as a reaction gas.

3 is a cross-sectional view illustrating a pad oxide film pattern and a hard mask pattern formed on a substrate.

Referring to FIG. 3, a pad oxide film (not shown) and a silicon nitride film for a hard mask (not shown) are formed on the semiconductor substrate 100.

The pad oxide layer may be formed at about 70 kPa to about 100 kPa through a thermal oxidation process, a chemical vapor deposition (CVD) process, or the like. The pad oxide layer may be about 750 ° C. for the surface treatment of the semiconductor substrate 100. To 900 ?? It can be formed at a temperature of about, and is formed to reduce the stress generated when the silicon nitride film is in direct contact with the semiconductor substrate 100.

In addition, the silicon nitride film is about 1500 kPa through a low pressure chemical vapor deposition (LPCVD) process or a plasma enhanced chemical vapor deposition (PECVD) process using gas, SiH4 gas, NH3 gas, or the like. It may be formed to a thickness of a degree.

In this case, an organic anti-reflection layer (ALL, not shown) may be further formed on the hard mask layer. The sustained antireflection film is a film provided to prevent the photoresist sidewall profile from being degraded by diffuse reflection in a subsequent photographic process.

Subsequently, a photoresist pattern (not shown) is formed on the silicon nitride layer, the silicon nitride layer is etched using the photoresist pattern as an etch mask to form a hard mask pattern 104, and the pad oxide layer is subsequently etched. The pad oxide film pattern 102 is formed. Examples of the etching process include a dry etching process using a plasma, a reactive ion etching process, and the like.

The hard mask pattern 104 and the pad oxide layer pattern 102 are formed to selectively expose portions of the semiconductor substrate 100 corresponding to the field regions.

4 is a cross-sectional view illustrating a trench formed by the hard mask pattern illustrated in FIG. 3.

Referring to FIG. 4, the photoresist pattern formed on the hard mask pattern 104 is removed through an ashing process or a strip process. Next, the trench 106 may be formed by selectively etching the exposed region of the semiconductor substrate 100 using the hard mask pattern 104 as an etching mask. In this case, the organic anti-reflection film is removed during the etching of the semiconductor substrate 100.

FIG. 5 is a cross-sectional view for describing a heat treatment process of the trench illustrated in FIG. 4.

Referring to FIG. 5, the substrate on which the trench is formed is transferred to a process chamber and heat treated at a temperature of about.

The heat treatment process increases the temperature of the substrate to 400 to 1,000 ° C., thereby densifying the subsequently formed helium liner oxide film. Therefore, the hydrogen is prevented from diffusing during the high-density plasma process using the hydrogen gas that proceeds as a reaction gas. By increasing the plasma power and reaction time in the chamber for forming the helium liner oxide film, the temperature of the substrate is increased.

FIG. 6 is a cross-sectional view illustrating a helium oxide film formed on the trench illustrated in FIG. 5.

Referring to FIG. 6, a helium oxide layer 108 is formed along a profile of the trench by performing a high density plasma process using helium gas as a reaction gas on a substrate heat-treated at a temperature of about 400 to 1,000 ° C. FIG. The helium oxide film is densified as the temperature of the substrate increases.

Then, the bias power is applied to more than 0 and less than 5000W. The bias power may not be applied in some cases. At this time, the source power in the chamber is applied 3000 to 4000 W for about 3 to 4 minutes.

The helium oxide film 108 is formed substantially uniformly with a thin thickness of about 300 kPa to 400 kPa, so that a space for forming a silicon oxide film to completely fill the trench is formed by a subsequent process. The helium oxide film is formed to reduce the internal stress of the silicon oxide film for device isolation embedded in the trench 106 by a subsequent process, and to prevent impurity ions from penetrating into the field region.

FIG. 7 is a cross-sectional view illustrating a silicon oxide film formed in a trench in which a helium oxide film shown in FIG. 6 is formed.

Referring to FIG. 7, a silicon oxide film 110 having excellent gap filling characteristics is deposited by a high density plasma chemical vapor deposition method to fill the trench 106 in which the helium oxide film 108 is formed. At this time, the silicon oxide film 110 is formed by generating plasma using hydrogen gas as the reaction gas. In this case, the silicon oxide film 110 formed is a stoichiometrically stable silicon oxide film as SiO ₂ , and the silicon overoxide to be described later is SiOx, where x is less than 2, and the silicon overoxide is stoichiometrically unstable. Means.

Here, the hydrogen gas may be used as a gas for creating a plasma atmosphere, the hydrogen gas is superior to the helium gas used in the prior art, and because the particles are very small, the gap filling ability is excellent because of this.

When the high density plasma process is performed at such a high bias, the silicon oxide film 110 having good gap filling characteristics may be formed. In more detail, since the deposition rate of the silicon oxide film 110 at the edge of the trench 106 is faster than the deposition rate at the bottom or sidewall of the trench 106, voids or seams are formed in the trench 106. Happens. Therefore, when the hydrogen gas having excellent straightness and very small particles is used, the silicon oxide film 110 having good gap filling characteristics can be prevented since it is not deposited from the side of the trench 106 and thus formation of voids or cores can be prevented. Can be formed.

FIG. 8 is a cross-sectional view for describing a silicon oxide film pattern formed from the silicon oxide film shown in FIG. 7.

Referring to FIG. 8, the silicon oxide film 110 is subjected to a chemical mechanical polishing (CMP) process to expose an upper portion of the hard mask pattern 104 to form a silicon oxide film pattern 112. Subsequently, although not shown in detail, the hard mask pattern 104 is removed to separate the device. In this case, the exposed semiconductor substrate 100 is an active region for forming a semiconductor device, and the silicon oxide layer pattern 112 is a field region for isolating the active regions.

Although not shown in detail, in a subsequent process, a transistor forming process including a gate oxide film (not shown) and a gate electrode (not shown) may be performed to form a gate electrode (not shown).

As described above, according to a preferred embodiment of the present invention, in the process of forming a silicon oxide film to be embedded in the trench by performing a high-density plasma process, after the substrate is heated to form a densified helium oxide film, the gap filling capability is A good hydrogen source gas is used to improve the buried capability of the trench without the occurrence of voids or shims. In addition, the helium oxide film prevents the hydrogen gas from diffusing to the substrate to generate an active pating phenomenon.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (3)

Heating the substrate having the trench for device isolation to a temperature of at least 400 ° C .; Performing a high density plasma process using a reaction gas containing helium (He) gas on the heated substrate to continuously form a helium oxide film on the bottom and side surfaces of the trench; And And forming a hydrogen oxide film filling the trench by performing a high density plasma process using a reaction gas including hydrogen (H ₂ ) gas on the helium oxide film. 2. The method of claim 1, wherein the helium oxide film is formed to a thickness of 300 kPa to 400 kPa. The method of claim 1, wherein the trench, Sequentially depositing a pad oxide film and a hard mask layer on the substrate; Patterning the hard mask layer and the pad oxide layer to form a hard mask pattern and a pad oxide layer pattern; And And etching the substrate by using the hard mask pattern as an etch mask.

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