KR20080002614A - Method for fabricating isolation layer of semiconductor device - Google Patents

Abstract

A method for forming an isolation layer of a semiconductor device is provided to nitridize a sidewall oxide layer exposed by loss of a liner nitride layer and to induce formation of an oxynitride layer on the sidewall of a trench by performing an annealing process in an atmosphere of a high-temperature NH3 gas or NO gas. A nitride layer pad is formed on a semiconductor substrate(100). The semiconductor substrate is selectively etched to form a trench(101) by using the nitride layer pad as an etch mask. A sidewall oxide layer(310) and a liner nitride layer(330) are sequentially formed in the trench. A first HDP(high density plasma) oxide layer(410) is deposited to partially fill the trench. The first HDP oxide layer is wet-etched. An annealing process using a nitrogen-including atmosphere is performed on a lost portion of the liner nitride layer at the upper sidewall of the trench. A second HDP oxide layer is formed on the etched first HDP oxide layer to fill the trench. In the annealing process, a portion of the sidewall oxide layer exposed by the loss of the liner nitride layer can be nitridized to form a silicon oxynitride layer.

Description

Method for fabricating isolation layer of semiconductor device

1 and 2 are cross-sectional views schematically illustrating a method of forming a device isolation of a conventional semiconductor device.

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor devices, and more particularly, to a method for forming isolation between semiconductor devices.

As the cell size of the semiconductor device is reduced and the necessity of high integration is required, the space between the device and the device for forming the device isolation film is very narrow. Accordingly, in order to effectively form a device isolation film in a narrow space, Shallow Trench Isolation (STI) is introduced, and high density plasma (HDP) having excellent trench fill capability is introduced. Plasma) oxide film is used. Moreover, recently, in order to further increase the filling capability of the HDP oxide, a DWD method of primary HDP deposition + wet etching + secondary HDP deposition has been proposed.

1 and 2 are cross-sectional views schematically illustrating a method of forming a device isolation of a conventional semiconductor device.

Referring to FIG. 1, in the conventional device isolation forming method, a buffer oxide film 21 and a nitride film pad 25 having a predetermined thickness are sequentially formed on an upper surface of a silicon semiconductor substrate 10, and a photolithography process is performed. Patterning by using Subsequently, the trench 11 is formed by etching the lower semiconductor substrate 10 using a dry etching method using the pattern of the residual nitride film pad 25 as an etching mask.

Subsequently, a sidewall oxide film 31, which is used for protecting the sidewalls of the trench 11 and the bottom portion of the silicon substrate 10, is formed to have a predetermined thickness or more using a thermal oxidation method or the like. A liner nitride layer 33 is chemically vapor deposited on the sidewall oxide layer 31. The liner nitride film 33 is understood to play an important role in relieving stress associated with the silicon substrate 10 to improve the refresh characteristics of the device.

Thereafter, the first HDP oxide layer 41 filling the trench 11 is deposited. At this time, the deposition thickness is appropriately adjusted to a predetermined thickness or less so that the trench 11 is not completely filled by the first HDP oxide film 41. A portion of the first HDP oxide layer 41 is removed by a wet etching method using an etching solution such as hydrofluoric acid (HF) or a buffer oxide etchant (BOE).

The purpose of the wet etching is to completely remove the portion of the first HDP oxide layer 41 formed on the sidewalls of the trench 11 and to leave only a portion of the portion of the first HDP oxide layer 41 embedded in the bottom of the trench 11, as shown in FIG. 2. Likewise, the trench 11 is better filled by the subsequent deposition of the second HDP oxide layer 43 to prevent filling defects such as voids and the like.

However, during the wet etching process, partial consumption or loss of the liner nitride layer 33 may occur in the exposed portion due to the etching by the HF or BOE solution. This liner nitride film 33 is consumed or lost, so that the liner nitride film 33 is formed to be much thinner than the thickness of the portion of the first HDP oxide film 41 to be wet-removed, thereby removing the first HDP oxide film 41. It can be understood that it is due to performing wet etching for a considerable time. Accordingly, as the wet etching time is increased, the consumption of the liner nitride layer 33 may be further increased.

Plasma ions accompanying the deposition of the second HDP oxide layer 43 are formed in the active region of the upper portion of the trench 11 where the lower sidewall oxide layer 31 is exposed by the loss of the liner nitride layer 33. Plasma damage (15) may occur due to the like.

Such plasma damage 15 may be understood as a factor that degrades various electrical characteristics of the semiconductor device. In particular, the leakage current of the gate oxide film introduced into the transistor may be increased, thereby degrading the gate oxide integration characteristic (GOI). In addition, by increasing the leakage current in the junction portion of the region in which the capacitor (DRAM) of the DRAM device is formed may act as a factor that degrades the refresh characteristics.

An object of the present invention is to provide a method for forming a device isolation of a semiconductor device to prevent plasma damage in the active region of the semiconductor substrate.

An aspect of the present invention for achieving the technical problem, forming a nitride film pad on a semiconductor substrate, selectively etching the portion of the semiconductor substrate using the pad nitride film pad as an etching mask to form a trench, the trench Sequentially forming a sidewall oxide film and a liner nitride film therein, depositing a first high density plasma (HDP) oxide film partially filling the trench, wet etching the first high density plasma oxide film, the wet etching by the wet etching Performing annealing using an atmosphere containing nitrogen on a portion of the upper sidewall portion of the trench where the liner nitride film is lost, and a second high density filling the trench on the etched first high density plasma oxide film A device of a semiconductor device comprising the step of forming a plasma oxide film Propose a re-forming method.

The atmosphere of the heat treatment may include a nitrogen oxide (NO) gas or a nitrogen trihydride (NH ₃ ) gas.

The heat treatment may be performed to nitride the sidewall oxide film portion exposed by the loss of the liner nitride film to form a silicon oxynitride film.

The heat treatment may be performed at a high temperature furnace of about 800 ° C. to 1000 ° C. for at least 30 minutes to form the silicon oxynitride film.

The heat treatment may be performed by rapid heat treatment (RTP) for at least 30 seconds to about 900 ℃ to 1100 ℃ to form the silicon oxynitride film.

According to the present invention, it is possible to provide a device isolation formation method of a semiconductor device for preventing plasma damage in an active region of a semiconductor substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and the like of the elements in the drawings are exaggerated to emphasize a more clear description, and the elements denoted by the same reference numerals in the drawings means the same elements.

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

Referring to FIG. 3, in the device isolation forming method according to an embodiment of the present invention, a buffer oxide film 210, a nitride film pad 250, and a photoresist pattern having a predetermined thickness are formed on the silicon semiconductor substrate 100. 270 are formed sequentially. Thereafter, the nitride film pad 250 is patterned by performing a selective etching process using the photoresist pattern 270 as an etch mask. Then, after removing the photoresist pattern 270, by using the pattern of the residual nitride film pad 250 as an etching mask to selectively etch the exposed semiconductor substrate 100 using a dry etching method for a trench for STI ( 101).

Referring to FIG. 4, the sidewall oxide film 310, which is used to protect portions of the silicon substrate 100 on the sidewalls and the bottom of the trench 101, is formed to have a predetermined thickness or more using a thermal oxidation method. A liner nitride layer 330 is deposited on the sidewall oxide layer 310 by CVD or the like. The liner nitride layer 330 may be understood to play a role of improving the refresh characteristics of the device by relieving stress accompanying the silicon substrate 100.

Thereafter, the first HDP oxide layer 410 filling the trench 101 is deposited. At this time, the deposition thickness is appropriately adjusted to a predetermined thickness or less so that the trench 101 is not completely filled by the first HDP oxide film 410. That is, the first HDP oxide layer 410 is deposited to partially fill the trench 101.

Referring to FIG. 5, the first HDP oxide layer 410 is wet etched by a wet etching method using an etching solution such as hydrofluoric acid (HF) or a buffer oxide etching solution (BOE). In this case, the wet etching is performed such that the first HDP oxide layer 410 does not remain in the upper sidewall portion of the trench 101. Accordingly, a portion of the liner nitride film 330 on the upper sidewall portion of the trench 101 may be exposed and lost. As a result, a portion of the sidewall oxide layer 310 on the upper sidewall portion of the trench 101 is exposed.

The purpose of the wet etching is to completely remove the portion of the first HDP oxide layer 410 formed on the sidewalls of the trench 101 and to leave only a portion of the portion of the first HDP oxide layer 410 embedded in the bottom of the trench 101, FIG. 7. As shown in FIG. 6, the trench 101 is better filled by subsequent deposition of the second HDP oxide layer 430 to prevent filling defects such as voids and the like.

As the wet etching process proceeds, partial consumption or loss of the liner nitride layer 330 may occur in the exposed portion due to the etching by the HF or BOE solution. In order to prevent plasma damage (15 in FIG. 2) caused by plasma ions or the like accompanying the second HDP oxide layer 430 deposition in the active region due to the loss of the liner nitride layer 330, as shown in FIG. 6. Heat treatment is performed in an atmosphere containing nitrogen.

Referring to FIG. 6, an atmosphere including a nitrogen atmosphere, for example, a nitrogen oxide (NO) gas or a nitrogen trihydride (NH ₃ ) gas, is introduced on the sidewall oxide film 310 where the liner nitride film 330 is lost and exposed. Then, annealing is performed to cause a decomposition reaction on the gas containing nitrogen. Nitrogen ions are generated by the decomposition reaction, and the ions react with the exposed sidewall oxide layer 310 to form a film 311 of a silicon oxynitride (SiON) -based oxynitride compound.

To this end, the heat treatment may be sufficiently performed at a high temperature furnace of about 800 ° C. to 1000 ° C. for at least 30 minutes to form the silicon oxynitride film 311. Alternatively, the heat treatment may be performed for a sufficient time by rapid heat treatment (RTP) for at least 30 seconds at about 900 ° C to 1100 ° C to form the silicon oxynitride film 311.

Referring to FIG. 7, after performing a nitrogen atmosphere heat treatment, a second high density plasma oxide layer 430 is formed on the etched first high density plasma oxide layer 410 to completely fill the trench 101. In this case, since the liner nitride layer 330 is lost, the silicon oxynitride layer 311 is modified, and thus plasma damage due to plasma ions accompanying deposition of the second HDP oxide layer 430 may be prevented. That is, the silicon oxynitride film 311 may be understood to play a role in blocking plasma ions from penetrating into the active region of the semiconductor substrate 100.

Thereafter, the second high density plasma oxide film 430 is planarized by chemical mechanical polishing (CMP) or the like to form a device isolation film separated for each trench 101. Afterwards, the nitride film pad 250 and the like exposed are selectively removed to form an isolation layer structure.

According to the present invention described above, it is possible to prevent the plasma damage caused by the partial loss of the liner nitride film caused in the process of forming the device isolation layer using the HDP oxide film, in particular the process of forming the STI structure of the DWD method. In other words, by annealing in a high temperature NH ₃ gas atmosphere or an NO gas atmosphere, the sidewall oxide film portion which is lost due to the loss of the liner nitride film may be nitrided, and eventually, the oxynitride film may be formed on the trench sidewall.

Accordingly, the penetration of plasma ions involved in the second HDP oxide film deposition process proceeded to the subsequent process is effectively suppressed by the oxynitride film. Due to the plasma damage suppression effect of the active region, the leakage current of the device formed in the active region is reduced, and thus the GOI characteristic and the refresh characteristic can be improved. Therefore, the effect of increasing the semiconductor device manufacturing yield can be realized.

As mentioned above, although this invention was demonstrated in detail through the specific Example, this invention is not limited to this, It is clear that the deformation | transformation and improvement are possible by the person of ordinary skill in the art within the technical idea of this invention.

Claims (5)

Forming a nitride film pad on the semiconductor substrate; Selectively etching the semiconductor substrate portion using the pad nitride film pad as an etch mask to form a trench; Sequentially forming a sidewall oxide film and a liner nitride film in the trench; Depositing a first high density plasma (HDP) oxide film partially filling the trench; Wet etching the first high density plasma oxide film; Performing annealing using an atmosphere containing nitrogen on a portion where the liner nitride film of the upper sidewall portion of the trench is lost; And And forming a second high density plasma oxide layer filling the trench on the etched first high density plasma oxide layer. The method of claim 1, The atmosphere of the heat treatment is a device isolation forming method of a semiconductor device, characterized in that it comprises a nitrogen oxide (NO) gas or nitrogen trihydride (NH ₃ ) gas. The method of claim 1, And the heat treatment is performed to nitride the sidewall oxide film portion exposed by the loss of the liner nitride film to form a silicon oxynitride film. The method of claim 3, Wherein the heat treatment is performed at a high temperature furnace of about 800 ° C. to 1000 ° C. for at least 30 minutes to form the silicon oxynitride film. The method of claim 3, Wherein the heat treatment is performed by rapid heat treatment (RTP) for at least 30 seconds at about 900 ° C. to 1100 ° C. to form the silicon oxynitride film.

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