KR20080101384A - Method for forming thin film of semiconductor devices - Google Patents

Abstract

A method for forming a thin film of a semiconductor device is provided to obtain a thin film of which morphology is excellent at a design tool of below 0.1 micrometer by using an ALD(Atomic Layer Deposition) technology instead a CVD(Chemical Vapor Deposition) technology when forming Ti/TiN film. A semiconductor substrate is mounted at an ALD(Atomic Layer Deposition) reaction chamber, and a Ti film is formed on the semiconductor substrate by using an ALD(Atomic Layer Deposition) technology. The semiconductor substrate at which the Ti film is formed is mounted at an additional reaction chamber, and an interface TiN film is formed by nitriding the surface of the Ti film at the atmosphere of NH3 gas. An upper TiN film is formed on the interface TiN film by using a CVD(Chemical Vapor Deposition) technology.

Description

Method for forming thin film of semiconductor devices

1 is a process flow diagram illustrating a thin film formation method according to the conventional ALD technology.

2 is a process flowchart showing thin film forming methods according to embodiments of the present invention.

3 shows XRD spectra of Ti / TiN films formed according to conventional ALD techniques and embodiments of the present invention, respectively.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor devices, and more particularly to a method of forming a Ti / TiN film of a semiconductor device.

In recent years, densification and high integration have accelerated in the manufacture of semiconductor devices. In response to this, multilayer wiring structures have become common. In order to form the multilayer wiring structure, a technique of embedding a metal material in a connection hole such as a contact hole or a via hole is important. As the metal material, a single metal such as aluminum (Al), copper (Cu), tungsten (W) and alloys thereof are used. In this case, it is common to form a Ti / TiN film between the silicon substrate and the metal material to prevent diffusion of components of the metal material into the silicon substrate. To this end, it is generally used to form a Ti film on the inner wall of the connection hole and to form a TiN film on the Ti film before filling the connection hole with the metal material.

Conventionally, the Ti / TiN film has been formed by using physical vapor deposition (PVD) or chemical vapor deposition (CVD). Among these, the PDV technology is difficult to achieve high step coverage, and thus, it is difficult to apply the present invention to the manufacture of modern high-integral semiconductor devices having strict design rules.

Compared to the PDV technique, the CVD technique is widely used in recent years because it can form a thin film having excellent step coverage. However, the demand for higher performance of semiconductor devices has increased, and the design rules of 0.1 [mu] m or less have been generalized. Nowadays, the non-uniformity of the morphology of thin films formed by the CVD technique has been highlighted.

In particular, in the conventional CVD technique using TiCl ₄ as a precursor, TiCl _x (x = 1 to 4) activated by plasma selectively etches silicon (Si), or excessively at a specific portion of the semiconductor substrate surface. Silicide may be formed. Accordingly, overgrowth or void may be formed on the semiconductor substrate.

Therefore, in the case of the Ti / TiN film formed by the CVD technique, the step coverage is low and the morphology of the design rule of 0.1 μm or less may be poor. In the case of the semiconductor device having the Ti / TiN film formed in the state of poor morphology, it may cause side effects such as an increase in resistance at the contact.

Recently, methods of forming thin films using atomic layer deposition (ALD) techniques have been reported. The ALD technology, unlike the PVD technology or the CVD technology, allows thin films to be formed only by complete surface reactions. Therefore, it can be said that it is an optimal method for obtaining a thin film excellent in morphology even in a design rule of 0.1 μm or less.

A method of forming a TiN film by the ALD technique is disclosed by Uhm et al. In Korean Patent No. 10-0665401 entitled "Method of Forming Titanium Nitride Film of Semiconductor Device". A method of forming a TiN film according to strictness is to repeat the ALD unit process consisting of four steps until the desired thin film thickness is formed.

However, unlike the formation of the TiN film disclosed by Um et al., Forming a Ti / TiN film by ALD technology can be expected to improve the morphology, but may cause problems related to the formation of pure Ti film.

1 is a process flow diagram illustrating a thin film formation method according to the conventional ALD technology.

Referring to FIG. 1, the conventional ALD technique is performed sequentially by dividing the entire process into an ALD process (S110) and a CVD process (S120). In order to proceed with the ALD process (S110), a semiconductor substrate is mounted in an ALD reaction chamber (S111).

The ALD unit reaction (S113) of forming a Ti thin film on the semiconductor substrate is repeated a plurality of times to form a Ti film having a desired thickness. (S115) The semiconductor substrate on which the Ti film is formed is in situ within the ALD reaction chamber. in-situ) to form an interfacial TiN film (S117).

In order to proceed with the CVD process (S120), the semiconductor substrate on which the interfacial TiN film is formed is transferred to a separate CVD reaction chamber (S121). In the CVD reaction chamber, the interfacial TiN film using a conventional CVD technique is used. An upper TiN film is formed on the substrate (S123).

In the case of forming the Ti / TiN film according to the conventional ALD technology, a problem of contamination of the ALD reaction chamber due to the residue of the reaction gas and the reaction by-product for forming the thin film may be raised. This is because NH _{3, which} is used as a reagent for forming a TiN film, may remain in the ALD reaction chamber through various processes, and it is not easy to remove the residual NH ₃ .

After the formation of the interfacial TiN film is completed, the residual NH ₃ is particularly problematic when a new Ti film is formed on a separate semiconductor substrate using the ALD reaction chamber contaminated by the interfacial TiN film formation process. This is because, when the new Ti film is formed, a TiN material is generated as a by-product by the residual NH ₃ instead of the pure Ti film, whereby a Ti film contaminated with the TiN component may be formed. As a result, a Ti / TiN film having poor ohmic contact characteristics can be formed.

The technical problem to be achieved by the present invention is to improve the above-described problems of the prior art, while having a stable morphology that can be applied to design rules of 0.1 μm or less, the Ti film is not contaminated by nitrogen compounds. A thin film forming method for forming a TiN film is provided.

In order to achieve the above technical problem, the present invention provides a thin film formation method for forming a Ti / TiN film on a semiconductor substrate. The semiconductor substrate is mounted in an atomic layer deposition (ALD) reaction chamber. A Ti film is formed on the semiconductor substrate using ALD technology. The semiconductor substrate on which the Ti film is formed is mounted in a separate chemical vapor deposition (CVD) reaction chamber. The surface of the Ti film is nitrided using plasma CVD technology to form an interfacial TiN film. An upper TiN film is formed on the interfacial TiN film by using a plasma CVD technique.

In other embodiments, in order to form the Ti film using the ALD technology, the ALD unit reaction consisting of the following four steps may be repeated one or more times. The ALD unit reaction may include a first step of forming an adsorption layer containing Ti atoms on the semiconductor substrate by injecting TiCl ₄ gas into the ALD reaction chamber, a second step of purging the ALD reaction chamber, Injecting H ₂ gas into the ALD reaction chamber to react with the adsorption layer to form a Ti thin film, and a fourth step of purging the ALD reaction chamber.

In another embodiment, an inert gas may be injected into the ALD reaction chamber in the first to fourth steps of the ALD unit reaction.

In another embodiment, H ₂ gas may be injected into the ALD reaction chamber in the first step of the ALD unit reaction.

In still other embodiments, the semiconductor substrate on which the Ti film is formed may be mounted in a CVD reaction chamber. The interfacial TiN film may be formed by nitriding the surface of the Ti film by injecting H ₂ gas, NH ₃ gas, and an inert gas into the CVD reaction chamber.

In another embodiment, TiCl ₄ gas, H ₂ gas, NH ₃ gas, and an inert gas are injected into the CVD reaction chamber on which the semiconductor substrate on which the interfacial Ti film is formed is injected, and the upper TiN layer is formed on the interfacial TiN film. A film can be formed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete, and that the spirit of the present invention to those skilled in the art will fully convey. Where a layer is said to be "on" another layer or substrate it may be formed directly on the other layer or substrate or a third layer may be interposed therebetween. Portions denoted by like reference numerals denote like elements throughout the specification.

2 is a process flowchart showing thin film forming methods according to embodiments of the present invention.

Referring to FIG. 2, the thin film forming method according to the exemplary embodiments of the present invention may be sequentially divided into an ALD process (S210) and a CVD process (S220). In order to proceed with the ALD process (S210), a semiconductor substrate may be mounted in the ALD reaction chamber. (S211) The semiconductor substrate may be formed with predetermined functional elements on a silicon wafer. Purging may be performed by supplying H ₂ gas and Ar gas to the ALD reaction chamber. In this case, the semiconductor substrate may be heated and maintained at 200 ° C. to 700 ° C. FIG.

A first reaction gas may be injected into the ALD reaction chamber purged and heated. The first reaction gas may be made of TiCl ₄ gas and Ar gas. The first step S213a of the ALD unit reaction S213 may be performed by applying a high frequency discharge using an RF generator to the inside of the reaction chamber to generate a first plasma. The first step S213a may be performed for 0.1 second to 20 seconds. Alternatively, the first step S213a may be performed by supplying TiCl ₄ gas, H ₂ gas, and Ar gas to the ALD reaction chamber and applying a high frequency discharge.

The second step (S213b) may be performed by stopping supply of the TiCl ₄ gas to the ALD reaction chamber and purging by supplying H ₂ gas and Ar gas. During the second step S213b, the TiCl ₄ gas and the reaction byproduct remaining in the ALD reaction chamber may be discharged to the outside.

Subsequently, a third step S213c of the ALD unit reaction S213 may be performed. In the third step (S213c), a second plasma can be generated by injecting a second reaction gas and applying a high frequency discharge to the ALD reaction chamber. The second reaction gas may be made of H ₂ gas and Ar gas. The third step S213c may be performed for 0.1 second to 20 seconds.

After the third step S213c, a fourth step S213d of the ALD unit reaction S213 may be performed. In the fourth step S213d, the high frequency discharge may be stopped and only H ₂ gas and Ar gas may be supplied. During the fourth step S213d, the TiCl ₄ gas and the reaction by-product remaining in the ALD reaction chamber may be discharged to the outside.

Whenever the ALD unit reaction (S213) that is continuously performed from the first step (S213a) to the fourth step (S213d) is performed once, a Ti film having an atomic size thickness can be stacked on the semiconductor substrate. The ALD unit reaction (S213) may be repeatedly performed until the Ti film is accumulated and formed to a predetermined thickness.

When the ALD process S210 is completed, the CVD process S220 may be performed. The semiconductor substrate having the Ti film formed in the ALD reaction chamber may be taken out of the ALD reaction chamber and mounted in the CVD reaction chamber (S221).

In the CVD reaction chamber, the Ti film may be treated in an NH ₃ atmosphere to form an interfacial TiN film. (S223) The treatment process in the NH ₃ atmosphere may include H ₂ gas, Ar gas, and NH ₃ in the CVD reaction chamber. This can be carried out by high frequency discharge while supplying gas. A third plasma may be generated according to the high frequency discharge to nitride the upper portion of the Ti film on the semiconductor substrate. Accordingly, the upper portion of the Ti film may be converted into an interfacial TiN film.

Subsequently, by forming an upper TiN film on the interfacial TiN film, the formation process of the Ti / TiN film according to the present invention can be completed. The formation of the upper TiN film (S225) may be performed in-situ using the CVD reaction chamber used to form the interfacial TiN film, or may be performed using another separate CVD reaction chamber. Specifically, the upper TiN film may be formed by applying a high frequency discharge while supplying TiCl ₄ gas, H ₂ gas, Ar gas, and NH ₃ gas to the CVD reaction chamber to generate a fourth plasma.

In contrast to the conventional CVD technology, the improvement effect of the embodiments according to the present invention using the ALD technology can be confirmed by scanning electron microscopy (SEM). In the case of the SEM photograph of the surface of the Ti film formed by using the CVD technique, the dents appear in various places on the surface of the Ti film. Such poor morphology can be observed through the irregularities of the surface in the SEM photograph of the cross section of the Ti film. In contrast, in the case of the Ti film according to the embodiment of the present invention to which the ALD technology is applied, it can be observed that the Ti film has a uniform morphology in both the surface SEM photograph and the cross-sectional SEM photograph.

3 illustrates X-ray diffraction spectra of Ti / TiN films formed according to conventional ALD techniques and embodiments of the present invention, respectively. In the XRD spectrum, the x-axis means 2θ indicating a multiple of the diffraction angle. Both the specimen according to the embodiment of the prior art and the specimen according to the embodiment of the present invention were prepared as a state of a partial Ti / TiN film, in which only a Ti film and an interfacial TiN film were formed on each semiconductor substrate.

Referring to FIG. 3, the difference between the spectrum 301 of the Ti / TiN film formed according to the conventional ALD technology and the spectrum 311 of the Ti / TiN film formed according to the present invention can be clearly seen.

As already mentioned above, the formation of the Ti / TiN film according to the present invention is performed separately in the ALD reaction chamber and the CVD reaction chamber, respectively. In contrast, in the conventional ALD technique, the formation of the Ti film and the formation of the interfacial TiN film are performed in-situ in the same ALD reaction chamber. In the prior art spectrum 301, peaks are formed at 2θ of 36.5 degrees and 42.9 degrees, respectively.

The peak 303 of 36.5 degrees indicates a crystal plane (hereinafter referred to as TiN [111] crystal plane) in which the Miller index of the Ti / TiN film is [111]. In addition, the peak 307 of 42.9 degrees can be identified as a TiN [200] crystal plane. The characteristic of the prior art spectrum 301 is that the characteristic peak is not seen at the 'where 2θ is 40.0 degrees' 305, which can be identified as the Ti [101] crystal plane indicating the formation of the Ti film among the Ti / TiN films. Is the point.

The peak indicating the formation of a pure Ti film in the prior art spectrum 301 may not be observed because the Ti film is contaminated by nitrogen-containing materials during the formation process of the Ti film. The contamination by the nitrogen-containing material in the conventional ALD technique may not be convinced at all in that the nitrogen-containing material is not used at all by the Ti film forming reaction itself. However, following the conventional ALD technique, the occurrence of contamination by the nitrogenous content can be observed consistently.

Referring back to FIG. 1, the contamination by the nitrogenous substance appearing in the application of the conventional ALD technology reacts to the formation process of the interfacial TiN film (S117 in FIG. 1) which is a process separate from the formation process of the Ti film. It may be due to the NH ₃ gas used as the agent. The NH ₃ gas is used as part of the reaction gas in the ALD process (S110 in FIG. 1), and may exist as residual NH ₃ in the ALD reaction chamber even after the reaction process in which the NH ₃ gas is used is completed. have.

It is noteworthy that, in contrast to the conventional ALD technique, when the conventional conventional CVD technique is applied, the residual NH ₃ gas does not interfere with the formation of the Ti film. The reason for this is because in the case of the conventional CVD technique, TiCl ₄ gas, continues to TiCl ₄ gas into the CVD reaction chamber for H ₂ gas, and the deposition reaction by the plasma of the Ar gas is supplied is formed. Therefore, the NH ₃ gas as a pollutant generated by evaporation of the residual NH ₃ is only a small amount compared to the TiCl ₄ gas supplied as a reactant in the Ti film forming process, and thus may not have a significant effect on the formation of the Ti film. have.

On the contrary, in the case of the conventional ALD technology, a result different from that of the conventional CVD technology may occur due to the characteristics of the ALD technology itself. In the conventional ALD technology, the third step is performed while only the H ₂ gas and the Ar gas are supplied while the TiCl ₄ gas is not supplied. During the third step, the residual NH ₃ is activated in an undesired plasma state to form a pure Ti film and reacts with a TiCl ₄ film having an atomic layer thickness formed on the semiconductor substrate to form a TiN film instead of the Ti film. have.

Therefore, in the conventional ALD technique in which the Ti film and the TiN film are in-situ, it is indispensable to remove the residual NH ₃ in the ALD reaction chamber to a very low level. However, the residual NH ₃ may exist in the form of reactants or by-products in the formation reaction of the Ti / TiN film and may be present in the physically adsorbed or chemisorbed state on the inner wall of the ALD reaction chamber. It is a problem because it is not removed.

Referring back to FIG. 3, unlike the prior art spectrum 301, the spectrum 311 of the present invention has a peak of 36.5 degrees (TiN [111] crystal plane; 313) and a peak of 42.9 degrees (TiN [ 200] crystal plane 317, as well as a 40.0 degree peak (Ti [101] crystal plane 315) clearly showing the formation of a pure Ti film. This, in the case of a Ti / TiN film formation process according to the present invention, Ti film formation, and interface between TiN film formed in a separate reaction chamber, the ALD reaction by each carried out in the chamber with the CVD reaction chamber due to the residual NH ₃ Ti film This is because contamination can be prevented at the source.

Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and may be modified in various other forms within the spirit of the present invention.

According to the embodiments of the present invention as described above, by using the ALD technology instead of the plasma CVD technology in the formation of the Ti / TiN film it is possible to obtain a thin film with excellent morphology in the design rule of 0.1 ㎛. In addition, unlike the conventional ALD technology in which the Ti film is formed on the Ti film in-situ after the Ti film is formed using the ALD reaction chamber, in the present invention, the formation of the interface TiN film is It is performed in a CVD reaction chamber separate from the ALD reaction chamber. Accordingly, in the formation of the Ti / TiN film according to the ALD technology, the problem of contamination of the Ti film due to residual NH ₃ can be solved.

Claims (6)

The semiconductor substrate is mounted in an atomic layer deposition (ALD) reaction chamber, Forming a Ti film on the semiconductor substrate using ALD technology; Mounting the semiconductor substrate on which the Ti film is formed in a chemical vapor deposition (CVD) reaction chamber, An interfacial TiN film is formed by nitriding the surface of the Ti film; And forming an upper TiN film on the interfacial TiN film. The method of claim 1, Forming the Ti film, Injecting TiCl ₄ gas into the ALD reaction chamber to form an adsorption layer containing Ti atoms on the semiconductor substrate; Purging the ALD reaction chamber; Injecting H ₂ gas into the ALD reaction chamber to react with the adsorption layer to form a Ti thin film; And And a fourth step of purging the ALD reaction chamber, wherein the first to fourth steps are repeated at least once. The method of claim 2, And injecting an inert gas into the ALD reaction chamber in the first to fourth steps. The method of claim 3, wherein And injecting H ₂ gas into the ALD reaction chamber in the first step. The method of claim 1, Forming the interfacial TiN film comprises injecting H ₂ gas, NH ₃ gas, and an inert gas into the CVD reaction chamber on which the semiconductor substrate on which the Ti film is formed is mounted. The method of claim 1, Forming the upper TiN film includes injecting TiCl ₄ gas, H ₂ gas, NH ₃ gas, and an inert gas into the CVD reaction chamber on which the semiconductor substrate on which the interfacial TiN film is formed is mounted.

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