KR20060123813A - Apparatus for forming of device isolation in a semiconductor device - Google Patents

Abstract

An isolation method for a semiconductor device is provided to improve a trench filling characteristic by using mixture gas including hydrogen source gas, oxygen source gas and silicon source gas as reaction gas in a high density plasma process for filling a silicon oxide layer in a trench. A high density plasma process using silicon source gas, oxygen source gas and hydrogen source gas as reaction gas is performed on a substrate having an isolation trench to form a first silicon oxide layer for filling the trench. A wet heat treatment is performed on the first silicon oxide layer at a temperature of around 400~1000 deg.C for a time interval of 30 minutes to convert the first silicon oxide layer into a second silicon oxide layer which is stoichiometrically stable. The second silicon oxide layer is polished to expose the upper part of the substrate so that an isolation layer pattern is formed.

Description

Apparatus for forming of device isolation in a semiconductor device

1 is a SEM photograph of a silicon oxide film containing silicon excess oxide.

FIG. 2 is a SEM photograph of a silicon oxide film subjected to a polishing process with respect to the silicon oxide film shown in FIG. 1.

3 to 7 are schematic cross-sectional views illustrating a device isolation method of a semiconductor device according to an embodiment of the present invention.

8 and 9 are schematic SEM photographs for comparing the trench gap filling characteristics according to the ratio of O _{2 in} the silicon oxide film.

10 is a graph illustrating the refractive index of the silicon oxide film according to the ratio of O ₂ and the presence or absence of heat treatment in the silicon oxide film.

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: thermal oxide film 110: nitrided liner

112: silicon oxide film 114: silicon oxide film 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 element isolation insulating film 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 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) deposition process. A mixed gas including a SiN ₄ source gas and an O ₂ source gas is used as a reaction gas of the deposition process, and a silicon oxide film (SiO ₂ ) is formed in the trench. In addition, He is used as a plasma atmosphere formation gas for forming the said plasma.

Meanwhile, during the deposition process, the larger the bias for forming the plasma, the better the gap-fill capability of the silicon oxide film filling the trench.

At this time, if the bias amount is increased to improve the gap filling capability of the silicon oxide film, the He gas may be sputtered into the semiconductor substrate and damage the semiconductor substrate. So, in place of the He gas to use H ₂ gas in order while using a high bias to prevent damage to the semiconductor substrate, and the H ₂ gas is the intensity of sputtering to the semiconductor substrate to a high bias smaller than He, the straightness Good gap filling properties are excellent.

However, the H ₂ gas easily reacts with O ₂ in the reaction gas, and reduces the ratio of O ₂ in the silicon oxide film to include silicon rich oxide in the silicon oxide film.

1 is a SEM photograph of a silicon oxide film containing silicon excess oxide.

Referring to FIG. 1, the portion A is a silicon excess oxide, which prevents device isolation between active and field regions during the polishing process.

In more detail, the silicon oxide film is usually polished to expose the semiconductor substrate to separate the device. That is, the device is separated into an active region (that is, an exposed semiconductor substrate) serving as a semiconductor element, and a field region (a silicon oxide film having a trench filled after the polishing process) for insulating the semiconductor elements. However, when the polishing process is performed on the silicon oxide film on which the silicon excess oxide is formed, the polishing process is not performed well by the silicon excess oxide (un-polishing), so that the active and field regions, that is, the semiconductor device cannot be separated. It will not function.

FIG. 2 is a SEM photograph of a silicon oxide film subjected to a polishing process with respect to the silicon oxide film shown in FIG. 1. Referring to FIG. 2, it can be seen that the silicon oxide film is un-polished due to the excessive silicon oxide.

An object of the present invention for solving the above problems is to provide a semiconductor device isolation method that does not contain a silicon excess oxide in the silicon oxide film is separated into active and field regions.

According to an aspect of the present invention for achieving the above object, by performing a high density plasma process using a reaction gas containing a silicon source gas, an oxygen source gas and a hydrogen source gas on a substrate formed with a trench for device isolation Forming a first silicon oxide film to fill the trench, and performing a wet heat treatment process on the first silicon oxide film to form the first silicon oxide film as a stoichiometrically stable second silicon oxide film, and the second silicon oxide film The upper surface of the substrate is polished to form an isolation pattern.

 The wet heat treatment may be performed at about 400 to 1000 ° C. for about 30 minutes.

According to the present invention as described above, by performing a high-density plasma process using a gas containing H ₂ , Si and O ₂ to form a silicon oxide film with good gap buried characteristics, and wet the silicon excess oxide contained in the silicon oxide film The annealing process converts into stoichiometrically stable silicon oxide, thus solving the problem of un-polishing due to excess silicon during polishing.

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.

3 to 7 are schematic cross-sectional views illustrating a device isolation method of a semiconductor device according to an embodiment of the present invention.

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 by a thermal oxidation process, and is formed to reduce stress generated when the silicon nitride layer is in direct contact with the semiconductor substrate 100. In addition, the silicon nitride film may be formed by a low pressure chemical vapor deposition (LPCVD) process.

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.

Next, 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. 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.

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.

In this case, after the trench 106 is formed, a thermal oxide film 108 and an insulating film liner 110 may be selectively formed. In more detail, a thermal oxide film 108 having a very thin thickness is formed by thermally oxidizing the trench surface to cure surface damage occurring during the previous dry etching process. Subsequently, an insulating film liner 110 is formed on the inner and bottom surfaces of the trench, on which the thermal oxide film 108 is formed, on the surfaces of the pad oxide film pattern 102 and the hard mask pattern 104 with a thickness of several hundred microseconds. do.

The insulating film liner 110 is formed to reduce stress in the silicon oxide film 112 for device isolation embedded in the trench by a subsequent process and to prevent impurity ions from penetrating into the field region. The insulating film liner 110 should be formed of a material having a high etching selectivity with the silicon oxide film 112 to be described later under specific etching conditions. For example, the insulating film liner 110 may be formed of silicon nitride (SiN).

Referring to FIG. 5, a silicon oxide film 112 having excellent gap filling properties is filled by the high density plasma chemical vapor deposition (HDP CVD) method to fill the trench 106. Preferably, the high density plasma oxide film 112 is formed by generating a plasma using SiH ₄ , O _2, and H ₂ gases as reaction gases. At this time, the high density plasma oxide film 112 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. It means an unstable state.

Here, the H ₂ gas may be used as a gas for creating a plasma atmosphere. The H ₂ gas has a higher straightness than the He gas used in the related art, and has a low sputtering strength on the semiconductor substrate 100. Can also be used at

When the high density plasma process is performed at such a high bias, the silicon oxide film 112 having good gap filling characteristics can be formed. In more detail, when a high bias is applied during the high density plasma process, the H ₂ gas having a good straightness goes straight to the bottom of the trench 106 and is not deposited from the side of the trench 106. The void formation can be prevented in advance, so that the silicon oxide film 112 having good gap filling characteristics can be formed.

At this time, the H ₂ gas used as the reaction gas and the plasma atmosphere forming gas reacts with O ₂ in the reaction gas to reduce the ratio of O ₂ in the silicon oxide film. That is, due to the reduction of O ₂ , the silicon oxide film 112 includes some silicon excess oxide in which silicon is excessively formed.

The silicon excess oxide acts as a difficulty of the polishing process, which will be described later. In more detail, the polishing conditions for performing the polishing process on the silicon oxide film 112 including the silicon excess oxide are conditions for polishing a silicon oxide film on which no silicon excess oxide is formed, that is, a stoichiometrically stable silicon oxide film. Is the same as Therefore, the slurry used for the silicon oxide film 112 containing the silicon excess oxide does not polish the silicon oxide, and because the slurry is polished for the same time at the same speed as when polishing the stoichiometrically stable silicon oxide film, The silicon oxide film 112 including the silicon excess oxide is not polished to the point where device isolation occurs.

Referring to FIG. 6, in order to convert the silicon oxide film 112, that is, SiOx (x <2), into a stoichiometrically stable SiO ₂ including a silicon excess oxide that acts as a difficulty during the polishing process as described above, the silicon The wet heat treatment is performed on the semiconductor substrate 100 having the silicon oxide film 112 including the excess oxide at about 400 to 1000 ° C. for about 30 minutes.

During the wet heat treatment, a silicon oxide film (SiOx) containing a silicon excess oxide is converted into a stoichiometrically stable silicon oxide film (SiO _2, 114). More specifically, the wet heat treatment is performed in water vapor, that is, H ₂ O atmosphere. Oxygen (O ₂ ) contained in the water vapor combines with silicon (Si) of the silicon overoxide in the silicon oxide film to convert the silicon overoxide (SiOx) into a stoichiometrically stable silicon oxide film (SiO ₂ , 114). .

Referring to FIG. 7, the silicon oxide film pattern 116 is formed by exposing an upper portion of the hard mask pattern 104 by performing a chemical mechanical polishing (CMP) process on the heat treated silicon oxide film 114. do. 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 116 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).

Hereinafter, the characteristics of the silicon oxide film and the silicon oxide film polishing process according to the experimental results will be described.

First, the results of comparative experiments on the trench gap filling ability according to the oxygen ratio included in the silicon oxide film will be described.

8 and 9 are schematic SEM photographs for comparing the trench gap filling characteristics according to the ratio of O _{2 in} the silicon oxide film.

8 and 9, it can be seen that the gap filling property when the ratio of O _{2 in} the reaction gas is 28 sccm is significantly lower than the gap filling property when 20 sccm. As described above, the ratio of oxygen (O ₂ ) is lowered and the gap filling characteristic is improved because of hydrogen (H ₂ ) bonded to the oxygen. The hydrogen gas has good straightness and hardly damages the semiconductor substrate even when a high bias is applied, thereby improving the gap filling characteristics of the silicon oxide film.

Hereinafter, the refractive index of the silicon oxide film according to the ratio of O ₂ and the presence or absence of heat treatment in the silicon oxide film containing silicon excess oxide will be described.

10 is a graph illustrating the refractive index of the silicon oxide film according to the ratio of O ₂ and the presence or absence of heat treatment in the silicon oxide film.

Referring to FIG. 10, it can be seen that the refractive index of the silicon oxide film is increased as the ratio of O ₂ in the silicon oxide film is lowered to 24, 20, and 16 sccm. Usually, the refractive index of the chemically stable silicon oxide film, that is, SiO ₂ film, is about 1.45 to 1.462. That is, when the refractive index is in the range of 1.45 to 1.462, it can be determined that the ratio of O _{2 in} the silicon oxide film is stoichiometrically stable. On the other hand, the refractive index of the silicon oxide film having an O ₂ ratio of about 16 sccm is about 1.465 to 1.7, and it is determined that the silicon oxide film having the above O ₂ ratio contains a silicon excess oxide.

Therefore, when the ratio of O _{2 in} the silicon oxide film is low as described above, by performing wet heat treatment, the ratio of O _{2 in} the silicon oxide film may be increased to form a stoichiometrically stable silicon oxide film.

As described above, according to a preferred embodiment of the present invention, in the process of forming a silicon oxide film to fill the inside of the trench by performing a high density plasma process, the reaction gas includes a hydrogen source gas, an oxygen source gas and a silicon source gas. The trench embedding characteristics are improved by using a mixed gas. In addition, the excess silicon oxide formed by reducing oxygen by the reaction of hydrogen and oxygen in the reaction gas is removed by performing a wet heat treatment process.

By removing the silicon excess oxide, the polishing process can be performed to the silicon oxide film to the polishing end point, so that the active and field regions can be reliably separated.

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 (6)

Forming a first silicon oxide film filling the trench by performing a high density plasma process using a silicon source gas, an oxygen source gas, and a hydrogen source gas as a reactive gas on a substrate on which a trench for device isolation is formed; Performing a wet heat treatment process on the first silicon oxide film to convert the first silicon oxide film into a stoichiometrically stable second silicon oxide film; And Forming an isolation layer pattern by polishing the second silicon oxide layer to expose an upper portion of the substrate. The method of claim 1, wherein the wet heat treatment is performed at a temperature of about 400 to 1000 ° C. for about 30 minutes. The method of claim 1, wherein the first silicon oxide film has a refractive index smaller than that of the second silicon oxide film. 4. The method of claim 3 wherein the second silicon oxide film has a refractive index of about 1.45 to 1.462. The method of claim 1, wherein the first silicon oxide film comprises silicon rich oxide. The method of claim 1, wherein the trench, Sequentially depositing a pad oxide film and a hard mask layer on the substrate; Forming a hard mask pattern and a pad oxide layer pattern by performing a photo process on the hard mask layer and the pad oxide layer; And And etching the substrate using the hard mask pattern as an etching mask.

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