KR20070066027A - Method for forming the isolation layer of semiconductor device - Google Patents

Abstract

A method for fabricating an isolation layer in a semiconductor device is provided to avoid generation of a moat by rounding the corner of an interface between an active region and an isolation region and by preventing a gap-fill oxide layer from being lost. A pad oxide layer(110) and a pad nitride layer are sequentially stacked on a silicon substrate(100) to form a pad pattern for defining an isolation region. A predetermined depth of the silicon substrate is etched to form a trench by using the pad pattern as an etch mask. A part of the pad oxide layer exposed through the trench is removed by a first blanket etch-back process using an HF solution as an etch solution. The pad nitride layer is removed by a second blanket etch-back process using an H3PO4 solution as an etch solution to expose a part of the end part of the pad oxide layer remaining after the first blanket etch-back process. The upper corner of the trench exposed through the residual pad oxide layer is rounded by a light etch process. A rounding oxide process is performed on the resultant structure to form a round oxide layer(140) on the inner wall of the trench. A gap-fill oxide layer(150) is filled in the trench having the round oxide layer.

Description

Method for forming the isolation layer of semiconductor device

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

2A through 2H are cross-sectional views sequentially illustrating a method of manufacturing a device isolation film of a semiconductor device according to an embodiment of the present invention.

 -Explanation of symbols for the main parts of the drawing-

100 silicon substrate 110 pad oxide film

120: pad nitride film 130: trench

140: rounding oxide film 150: gap fill oxide film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device isolation film manufacturing method of a semiconductor device, and more particularly, to prevents the formation of moat during shallow trench isolation (STI) process. And a device isolation film manufacturing method of a semiconductor device for improving reliability.

In general, in order to form transistors, capacitors, and the like on the silicon substrate, a silicon isolation region is formed in the silicon substrate to prevent the current from being electrically energized with the active region, and to separate the devices from each other.

In the step of forming the device isolation region, a trench having a constant depth is formed in the silicon substrate, a gapfill oxide film is embedded in the trench, and then an unnecessary portion of the gapfill oxide film is polished by a chemical mechanical polishing process. As a result, a shallow trench isolation (STI) process for forming an element isolation film in a silicon substrate has been widely used in recent years.

However, according to the device isolation film manufacturing method according to the prior art, during the pad nitride film removal process performed after the chemical mechanical polishing of the gap fill oxide film, the gap fill oxide film adjacent to the pad nitride film due to the excessive etching time according to the thickness of the pad nitride film There is also a problem in that a part of the edges of the side is also lost, causing moat.

Next, a device isolation film manufacturing method of a semiconductor device according to the prior art will be described with reference to the accompanying drawings.

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

First, as shown in FIG. 1A, a pad oxide film 110 and a pad nitride film 120, which are masks defining active regions and device isolation regions, are sequentially formed on the silicon substrate 100.

Then, the trench 130 is formed by etching the silicon substrate 100 by a predetermined depth using the pad nitride layer 120 as an etching mask. However, at this time, the upper edge of the trench 130, that is, the upper edge of the silicon substrate 100 on the interface between the active region and the isolation region has a problem that is formed in a sharp profile through the STI process.

Therefore, in the related art, as shown in FIG. 1B, a rounding oxidation process is performed on the silicon substrate 100 on which the trench 130 is formed to solve the above problem. The rounded oxide film 140 is formed on the inner wall of the. In this case, the rounding oxide layer 140 is a film formed by oxidizing a portion of the surface of the silicon substrate 100, which is an inner wall of the trench 130, so that the rounding oxide layer 140 may be rounded as “A” in the upper edge portion of the trench 130. Is formed.

Subsequently, as shown in FIG. 1C, the trench 150 is buried by thickly depositing the gap fill oxide film 150 on the entire surface of the product on which the rounding oxide film 140 is formed. However, at this time, the gap fill oxide film 150 buried in the gap formed between the rounding oxide film 140 and the pad nitride film 120 (see "A" in FIG. 1B) is buried elsewhere. Compared to the relative porosity (porous) characteristics.

In addition, the pad nitride layer 120 is used as an etch stop layer to chemically polish the gap fill oxide layer 150 to planarize the resultant.

Thereafter, as shown in FIG. 1D, the pad nitride film 120 is removed. At this time, the pad nitride film 120 is removed using a phosphoric acid solution, and the average pad nitride film 120 remaining since the thickness of the pad nitride film 120 remaining for each position of the silicon substrate due to the imbalance of the chemical mechanical smoke film is different. The pad nitride layer 120 is completely removed by immersing the silicon substrate in a phosphoric acid solution for a time that can be removed more than twice the thickness of the substrate.

However, when immersed in the phosphoric acid solution for a long time as described above, the gap-fill oxide film 150 buried in the gap between the rounding oxide film 140 and the pad nitride film 120 (see "A" of FIG. As a result, the etch rate is faster than that of the gap fill oxide film formed in the other region, and thus a moat occurs as shown in the boundary between the active region and the isolation region.

However, as described above, when the moat occurs at the boundary between the active region and the device isolation region, when the device is driven, the field crowding effect is added to the moat, so that the inverse narrow width effect (INWE) and the hump are increased. It causes abnormal operation of devices such as (hump).

Therefore, when the semiconductor device is manufactured according to the prior art, there is a problem in that the characteristics and reliability of the device are deteriorated.

Accordingly, an object of the present invention is to provide a method of manufacturing a device isolation film of a semiconductor device to form a rounded corner at the boundary point between the active region and the device isolation region, and to prevent the occurrence of moat to solve the above problems. have.

In order to achieve the above object, the present invention is a step of forming a pad pattern defining a device isolation region by sequentially depositing a pad oxide film and a pad nitride film on a silicon substrate, the silicon substrate is predetermined by using the pad pattern as an etching mask Etching to form a trench, removing a portion of the pad oxide layer exposed through the trench through a first front etch back process, and removing the pad nitride layer through the first front etch back process Removing a portion of the end portion of the oxide layer through a second front etch-back process to expose a portion of the oxide end portion; and etching and rounding an upper edge of the trench exposed through the remaining pad oxide layer; and forming the rounded trench. Forming a rounding oxide film on the inner wall of the trench by rounding oxidation Provided is a method of fabricating an isolation layer in a semiconductor device, the method including filling a gap fill oxide layer in a trench in which a ground oxide layer is formed.

In addition, in the device isolation film manufacturing method of the semiconductor device of the present invention, the first front etch back process, it is preferable to use the HF solution as an etching solution.

In addition, in the method of manufacturing a device isolation film of the semiconductor device of the present invention, the second front etch back process may preferably use a H ₃ PO ₄ solution as an etching solution, more preferably at a temperature of 150 ° C. or higher.

Further, in the device isolation film manufacturing method of the semiconductor device of the present invention, the light etching process of rounding the upper edge of the trench, dry etching using Cl ₂ / HBr gas, or a corrosion solution having excellent Si etching selectivity to SiO ₂ . It is preferable to use the wet etching.

Further, in the device isolation film manufacturing method of the semiconductor device of the present invention, after filling the gap fill oxide film in the trench formed with the rounding oxide film, the gap fill oxide film is chemically mechanically polished to the point where the pad nitride film is exposed to planarize the resultant product. Preferably, the method further includes removing the pad nitride film and pre-cleaning the product from which the pad nitride film has been removed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like parts throughout the specification.

A method of fabricating an isolation layer of a semiconductor device according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

2A through 2H are cross-sectional views sequentially illustrating a method of manufacturing a device isolation film of a semiconductor device according to an embodiment of the present invention.

First, as shown in FIG. 2A, the pad oxide film 110 and the pad nitride film 120 are sequentially formed on the silicon substrate 100.

Here, the pad oxide layer 110 is deposited to a thickness of about 100 GPa to relieve stress of the silicon substrate 100 and the pad nitride layer 120 and to remove the subsequent pad nitride layer 120 to serve as an etch stop layer. do. In addition, the pad nitride layer 120 may be deposited to a thickness of about 1000 μs and may be used as an etching mask in a subsequent trench etching process, or may be used as an etch stop layer in a chemical mechanical polishing process to planarize an insulating layer embedded in a subsequent trench. .

Then, a photoresist pattern (not shown) defining an isolation region is formed on the pad nitride layer 120, and then the pad nitride layer 120 and the pad oxide layer 110 are sequentially etched using the etching mask as an etching mask. A pad pattern exposing the upper surface of the silicon substrate 100 corresponding to the device isolation region is formed.

Next, the trench 130 is formed by etching the exposed silicon substrate 100 by a predetermined depth using the pad pattern as an etching mask. At this time, the upper edge of the trench 130, that is, the upper edge of the silicon substrate 100 at the interface between the active region and the isolation region is formed in a sharp profile through the STI process.

Subsequently, as illustrated in FIG. 2B, a first front etch back (eg, a portion of the pad oxide layer 110 exposed through the trench 130 may be secured to secure a space for rounding the upper edge of the trench 130). Pull Etch Back) process to remove. In this case, it is preferable to use an HF solution to selectively remove only the pad oxide layer 110 as an etching solution.

Then, as shown in FIG. 2C, a portion of the pad nitride layer 120 is exposed through a second front etch back process so that a portion of the end portion of the pad oxide film 110 remaining through the first front etch back process is exposed. Remove In addition, the second front etch-back process is preferably carried out by soaking in a phosphoric acid (H ₃ PO ₄ ) solution of 150 ° C or higher.

This causes the gapfill oxide film to be formed by the subsequent process to be formed on the upper edge of the silicon substrate 100 adjacent to the trench 130, thereby causing a problem as described above, namely "A" shown in FIG. 1B. To prevent it.

Next, as shown in FIG. 2D, the upper edge of the trench 130 exposed through the remaining pad oxide layer 110, that is, the upper edge of the silicon substrate 100 adjacent to the trench 130 is lighted. ) Etching is used to round the relatively protruding edges, such as "C". In this case, the light etching process may be dry etching using Cl ₂ / HBr gas having excellent etching selectivity of Si to oxide, or wet etching using a corrosion solution having excellent Si etching selectivity to SiO ₂ .

Subsequently, a rounding oxidation process is performed on the resultant product of the light etching process. Then, as shown in FIG. 2E, a rounding oxide layer 140 is formed on the inner wall of the trench 130 so that the upper edge of the trench 130 is rounded second. In this case, the rounding oxide layer 140 is a film formed by oxidizing a portion of the surface of the silicon substrate 100, which is an inner wall of the trench 130, to form a rounded upper edge portion of the trench 130.

Next, as shown in FIG. 2F, the trench 130 is buried by thickly depositing the gap fill oxide layer 150 on the entire surface of the resultant product in which the rounding oxide layer 140 is formed. At this time, the present invention is a pad nitride film 120 is removed through the second front etch back process, such as "D" to solve the conventional problem (see Fig. 1b) that the gap between the rounding oxide film 140 and the pad nitride film 120 Can be removed using the space of).

Subsequently, as illustrated in FIG. 2G, the gap nitride oxide film 150 is chemically mechanically polished using the pad nitride film 120 as a polishing stop film to planarize the resultant product.

Then, as shown in FIG. 2H, the remaining pad nitride film 120 is immersed in a phosphoric acid solution (H ₃ PO ₄ ) at 150 ° C. for a sufficient time and completely removed.

Subsequently, a pre-cleaning process is performed on the resultant product from which the pad nitride layer 120 is removed to improve the rounding profile of the upper edge of the gap fill oxide layer 150 and to remove the upper portion of the gap fill oxide layer 150. Alleviate the step between the separation zone and the active zone.

Therefore, in the present invention, as shown in "E" of FIG. 2H, a portion of the gap fill oxide film 150 having sharply formed corners and porous characteristics is lost at the boundary point between the active region and the device isolation region to generate a moat. Can be prevented.

As described above, the present invention can form a rounded corner at the boundary point between the active region and the device isolation region, and prevent the loss of the gapfill oxide film to block the generation of the moat.

Therefore, the present invention can also prevent the deterioration of the electrical characteristics of the device, such as the inverse narrow width effect (INWE) and the hump (Hump) caused by the moat to improve the characteristics and reliability of the device.

Claims (7)

Forming a pad pattern defining a device isolation region by sequentially depositing a pad oxide film and a pad nitride film on a silicon substrate; Etching the silicon substrate by a predetermined depth using the pad pattern as an etching mask to form a trench; Removing a portion of the pad oxide layer exposed through the trench through a first front etch back process; Removing the pad nitride film through a second front etch back process so that a portion of the end portion of the pad oxide film remaining through the first front etch back process is exposed; Light-etching and rounding an upper edge of the trench exposed through the remaining pad oxide layer; Forming a round oxide on the inner wall of the trench by rounding oxidation of the silicon substrate on which the rounded trench is formed; And And filling a gap fill oxide film in the trench in which the rounding oxide film is formed. The method of claim 1, The first front etch back process is a method of manufacturing a device isolation film of a semiconductor device, characterized in that using the HF solution as an etching solution. The method of claim 1, The second front etch back process is a method of manufacturing a device isolation film of a semiconductor device, characterized in that using the H ₃ PO ₄ solution as an etching solution. The method of claim 3, The second front etch-back process is a device isolation film manufacturing method of a semiconductor device, characterized in that at a temperature of 150 ℃ or more. The method of claim 1, The light etching process of rounding the upper edge of the trench, the method of manufacturing a device isolation film of a semiconductor device, characterized in that the dry etching using Cl ₂ / HBr gas. The method of claim 1, In the light etching process of rounding the upper edge of the trench, the method of manufacturing a device isolation film of a semiconductor device, characterized in that the wet etching using a corrosion solution having excellent Si etching selectivity to SiO ₂ . The method of claim 1, After the gapfill oxide is buried in the trench where the rounding oxide is formed Chemically polishing the gap fill oxide layer to a point where the pad nitride layer is exposed to planarize the resultant; Removing the pad nitride film; And And pre-cleaning the resultant product from which the pad nitride layer has been removed.

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