Method for fabricating a thin film and a metal line of a semiconductor device

A method for forming a thin film of a semiconductor device is provided. The method includes forming a TaN film on a semiconductor substrate by employing an atomic layer deposition method; and converting a part of the TaN film into a Ta by reacting the TaN film with NO2 to form a Ta film. The NO2 is formed by reacting NH3 with O2.

RELATED APPLICATION

This application is based upon and claims the benefit of priority to Korean Application No. 10-2005-0134357, filed on Dec. 29, 2005, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method for forming a metal line of a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device having a copper wiring.

BACKGROUND

With the realization of high-speed and highly integrated semiconductor devices, metal lines formed within the semiconductor devices are getting finer with multi layers. In such a case, the widths of the metal lines are decreased as well, thereby causing a signal delay due to the resistance and capacitance of the metal lines. Thus, to reduce such a signal delay, copper having a low resistance has been widely employed for the formation of the metal line.

In contrast to conventional metals employed, copper is difficult to etch. Accordingly, a copper wiring is formed through a damascene process including the steps of: forming a trench first; then forming a copper layer to fill the trench; and finally performing a chemical mechanical polishing thereon.

Since copper tends to diffuse into other layers easily, a barrier layer is formed on the trench before filling the trench with copper.

Though the barrier layer can be formed of Ta film, a Ta film cannot prevent the diffusion of copper perfectly. For this reason, the barrier layer has been formed of TaN. However, the TaN film is disadvantageous in that its adhesive strength with copper is low, though it can prevent the diffusion of copper more effectively than the Ta film.

Thus, nowadays, the barrier layer is formed of a dual film of Ta/TaN, so as to improve the reliability of the semiconductor device. The dual-film barrier layer can be formed by using a physical vapor deposition (PVD) process or an atomic layer deposition (ALD) process.

However, when the dual-film barrier layer is formed by the PVD process, an overhanging phenomenon may occur, in which an entrance of a via is blocked, if the aspect ratio (a ratio of a depth to a width) of the via is large, which results in a failure to form a barrier layer appropriately.

Meanwhile, when forming the dual-film barrier layer by the ALD method, a TaN film and a Ta film are formed by using different precursors, so the whole process becomes complicated. Furthermore, since carbon (C) and oxygen (O) are contained in the obtained TaN film, the resistivity of the TaN film is increased.

SUMMARY

Therefore, consistent with the present invention, there is provided a method for forming a dual film of Ta/TaN easily without causing an overhanging phenomenon.

In accordance with a first aspect consistent with the present invention, there is provided a method for forming a thin film of a semiconductor device. The method includes the steps of: forming a TaN film on a semiconductor substrate by employing an atomic layer deposition method; and converting a part of the TaN film into a Ta film by reacting the TaN film with NO2.

In accordance with a second aspect consistent with the present invention, there is provided a method for forming a metal line of a semiconductor device. The method includes the steps of: (a) forming an interlayer insulating film on a semiconductor substrate; (b) forming a trench on the interlayer insulating film; (c) forming a TaN film on the semiconductor substrate formed in step (b), the TaN film being formed of TaN by employing an ALD method; (d) converting a part of TaN film into a Ta film by reacting the TaN film with NO2; and (e) forming a metal line on the Ta film.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments consistent with the present invention will be described in detail with reference to the accompanying drawings so that the present invention may be easily implemented by those skilled in the art. However, it is to be appreciated that the present invention is not limited to the preferred embodiments and may be varied in various ways.

Referring toFIG. 1, there is provided a cross sectional view of a metal line112of a semiconductor device10consistent with a first preferred embodiment of the present invention.

As shown inFIG. 1, an etch stop layer104and an interlayer insulating film106are formed on a substrate100. Substrate100may include individual devices (not shown) or a lower conductor102.

Lower conductor102may be formed of copper (Cu), aluminum (Al), tungsten (W), silver (Ag), gold (Au), platinum (Pt), or the like. Etch stop layer104may be made of SiN, SiH4, or the like. Interlayer insulating film106may be formed by depositing an organic or inorganic insulating material, such as a fluorine silicate glass (FSG), an undoped silicate glass (USG), SiH4, and a tetra ethylortho silicate (TEOS) in a single layer or in multiple layers. Alternatively, interlayer insulating layer104may be formed of a low-k material, such as a black diamond (BD) having a dielectric constant not greater than a value of 3.0.

Formed through etch stop layer104and interlayer insulating film106is a trench T through which lower conductor102of substrate100is exposed.

Further, formed inside trench T are first and second barrier metal layers108and110, and metal line112that is electrically connected to lower conductor102.

Barrier metal layers108and110prevent a metal material of metal line112from being diffused into another layer such as an insulating film, while enhancing the adhesion of insulating film106and metal line112.

Further, first and second barrier metal layer108and110form a dual barrier structure together. First barrier metal layer108may be formed of TaN, while second barrier metal layer110may be formed of Ta. Metal line112may be formed of a conductive material such as copper having a low resistance.

Below, a method for forming metal line112of semiconductor device10ofFIG. 1will be explained with reference toFIGS. 2 and 3together withFIG. 1.

FIGS. 2 and 3provide cross sectional views to describe a method for forming metal line112of semiconductor device10inFIG. 1consistent with the first preferred embodiment of the present invention, wherein initial steps of the method are omitted.

As shown inFIG. 2, etch stop layer104and interlayer insulating film106are deposited on substrate100having lower conductor102. Then, trench T is formed on interlayer insulating film106through a selective etching process using a photoresist film (not shown) such that etch stop layer104is partially exposed through trench T.

Thereafter, the exposed part of etch stop layer104is removed, so that lower conductor102is partially exposed. Subsequently, TaN is deposited by using an Atomic Layer Deposition (ALD) method while maintaining substrate100at a temperature of about 250 to 300° C., thus obtaining first barrier metal layer108. First barrier metal layer108is formed to have a thickness of about 7 nm or less, preferably 1 nm.

As a reaction gas for forming first barrier metal layer108, ertbutylimido(trisdiethylamide)tantalum (TBTDET), pentakis(diethylamide)tantalum (PEEAT), pentakis(dimethylamide)tantalum (PDMAT), pentakis(ethylmethylamino)tantalum (PEAMT), or the like may be employed.

First barrier metal layer108thus formed may contain carbon (C) and oxygen (O).

Then, first barrier metal layer108is reacted with an oxidizing ammonia. As a result, N of first barrier metal layer108is removed, such that a part of first barrier metal layer108is converted into Ta, thereby forming second barrier metal layer110made of Ta, as shown inFIG. 3. First barrier metal layer108is reacted with the oxidizing ammonia until the thickness of second barrier metal layer110becomes approximately identical with that of first barrier metal layer108.

During this process, carbon (C) and oxygen (O) contained in first barrier metal layer108are also removed, so that TaN of the remaining first barrier metal layer108may have a higher purity.

NO2, which is formed by reacting NO3with O2at a high temperature, is employed as the oxidizing ammonia.

Then, referring back toFIG. 1, copper is deposited on second barrier metal layer110, so that a copper layer that fills trench T defined by second barrier metal layer110is obtained. Subsequently, by planarizing through a chemical mechanical polishing process, metal line112, and barrier metal layers108and110are finally obtained.

FIG. 4is a cross sectional view of a metal line212of a semiconductor device20consistent with a second preferred embodiment of the present invention.

As shown inFIG. 4, an etch stop layer204and an interlayer insulating film206are formed on a substrate200. Substrate200may include individual devices (not shown) or a lower conductor202.

Lower conductor202may be formed of copper (Cu), aluminum (Al), tungsten (W), silver (Ag), gold (Au), platinum (Pt), or the like. Etch stop layer204may be made of SiN, SiH4, or the like. Interlayer insulating film206may be formed by depositing an organic or inorganic insulating material, such as a fluorine silicate glass (FSG), an undoped silicate glass (USG), SiH4, and a tetra ethylortho silicate (TEOS) in a single layer or multiple layers. Alternatively, interlayer insulating film204may be formed of a low-k material, such as a black diamond (BD) having a dielectric constant not greater than a value of 3.0.

Formed in etch stop layer204and interlayer insulating film206is a via V through which lower conductor202of substrate200is exposed, and a trench T through which via V is exposed.

Further, deposited inside trench T and via V are first and second barrier metal layers208and210, and metal line212that are electrically connected to lower conductor202.

Barrier metal layers208and210prevent a metal material of metal line212from being diffused into another layer such as insulating film206, while enhancing the adhesion of insulating film206and metal line212.

Further, first and second barrier metal layers208and210form a dual barrier structure together. First barrier metal layer208is formed of TaN, while second barrier metal layer210is formed of Ta. Metal line212is made of a conductive material such as copper having a low resistance.

Below, a method for forming metal line212of semiconductor device20ofFIG. 4will be explained with reference toFIGS. 5 to 7together withFIG. 4.

FIGS. 5 to 7provide cross sectional views to describe a method for forming metal line212of semiconductor device20inFIG. 4consistent with the second embodiment of the present invention, wherein initial steps of the method are omitted.

As shown inFIG. 5, an etch stop layer204and an interlayer insulating film206are deposited on a substrate200having a lower conductor202.

Then, a via V for allowing etch stop layer204to be exposed therethrough is formed in interlayer insulating film206through a selective etching process using a photoresist film (not shown). Thereafter, a trench T is formed in interlayer insulating film206through a selective etching process using a photoresist film (not shown) such that via V is exposed through trench T. In case interlayer insulating film206is formed in a multiple of layers, one of the multi layers of interlayer insulating film206may be used as an etching stop layer when trench T is formed.

Thereafter, as illustrated inFIG. 6, exposed etching stop layer204is removed, so that lower conductor202is partially exposed. Subsequently, TaN is deposited by using an ALD process while maintaining substrate200at a temperature of about 250 to 300° C., thus obtaining a first barrier metal layer208. First barrier metal layer208is formed to have a thickness of about 7 nm or less, preferably 1 nm.

As a reaction gas for forming first barrier metal layer208, ertbutylimido (trisdiethylamide) tantalum (TBTDET), pentakis (diethylamide) tantalum (PDEAT), pentakis(dimethylamide)tantalum (PDMAT), pentakis (ethylmethylamino) tantalum (PEAMT), or the like may be employed.

First barrier metal layer208thus formed may contain carbon (C) and oxygen (O).

Then, first barrier metal layer108is reacted with an oxidizing ammonia. Substrate200is submerged in a diluted HNO3solution. As a result, N of first barrier metal layer208is removed, such that a part of first barrier metal layer208is converted into Ta, allowing a second barrier metal layer210made of Ta to be formed, as shown inFIG. 7. First barrier metal layer108is reacted with the oxidizing ammonia until the thickness of second barrier metal layer210becomes approximately identical with that of first barrier metal layer208.

During this process, carbon (C) and oxygen (O) contained in first barrier metal layer208are also removed, so that the TaN of remaining first barrier metal layer208may have a higher purity.

NO2, which is formed by reacting NO3with O2at a high temperature, is employed as the oxidizing ammonia.

Then, referring back toFIG. 4, copper is deposited on second barrier metal layer210, so that a copper layer that fills via V and trench T defined by second barrier metal layer210is obtained. Subsequently, by planarizing through a chemical mechanical polishing process, metal line212, and barrier metal layers208and210are finally obtained.

Consistent with the present invention as described above, it is possible to remove impurities contained in barrier metal layers when they are formed the ALD method. Therefore, the resistivity of the barrier film layers may be reduced. Further, the barrier film layers may have a higher density.

Moreover, since the Ta film may be easily formed from the TaN film, which is formed by the ALD method, the whole process for forming the thin films and the semiconductor device may be simplified by using a nitric acid solution.

While the invention has been shown and described with respect to the preferred embodiments, it is to be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.