Chemical vapor deposition apparatus, film forming method, and method of manufacturing semiconductor device

In forming a TiN film on a base material (10) by a MOCVD method, a space between a showerhead (3) and a trapping member (5) is heated by a heater (2) up to a temperature at which TDMAT is thermally decomposed, or higher. Next, source gas containing TDMAT, and so on are emitted from the showerhead (3) into a chamber (1). As a result, the TDMAT emitted into the chamber (1) is thermally decomposed into TiN, carbon, and hydrocarbon by the heater (2) in the space between the showerhead (3) and the trapping member (5). Then, the TiN, carbon, and hydrocarbon move toward the base material (10). Then, the carbon and hydrocarbon are trapped by the trapping member (5). On the other hand, the TiN passes through the trapping member (5) without being trapped to reach the base material (10). As a result, a TiN film containing neither carbon nor hydrocarbon grows on a surface of the base material (10).

TECHNICAL FIELD

The present invention relates to a chemical vapor deposition apparatus, a film forming method, and a method of manufacturing a semiconductor device which are suitable for forming a barrier metal film.

BACKGROUND ART

In forming wiring included in a semiconductor device, a barrier metal film such as a TiN film and a Ti film is formed. Examples of a method of forming the TiN film are a sputtering method, a MOCVD (Metal Organic Chemical Vapor Deposition) method, and the like. The MOCVD method has an advantage of high coverage.

In forming the TiN film by the MOCVD method, tetrakis (dimethylamino)titanium (TDMAT: Ti[N(CH3)2]4) is mainly used a raw material. TDMAT is especially effective when used after the formation of Al wiring because it is thermally decomposed at relatively low temperatures.

However, since TDMAT contains carbon, carbon and hydrocarbon are easily taken into the TiN film. The TiN film, when carbon or hydrocarbon is taken thereto, increases in specific resistance and thus cannot exhibit a desired characteristic.

Therefore, the conventional method has a process of removing carbon and hydrocarbon by irradiating a TiN film with plasma after forming the TiN film with a thickness of about 10 nm or less. A reason why the thickness of the TiN film is set to about 10 nm or less is that even the plasma irradiation cannot completely remove carbon and so on if the TiN film has a larger thickness than this. Incidentally, RF power for the plasma irradiation is about 750 W.

In this method, however, the number of processes increases as the thickness that the TiN film is required to have is larger. For example, when a TiN film with 20 nm is necessary, it is necessary to repeat the formation of the TiN film at least twice and the plasma irradiation at least twice. As an extreme example, when a TiN film with 100 nm is necessary, it is necessary to repeat the formation of the TiN film at least ten times and the plasma irradiation at least ten times. Therefore, it cannot be said that a throughput is sufficiently high. Further, as the number of times of the plasma irradiation increases, semiconductor elements such as transistors already formed are more damaged.

Increasing the RF power of the plasma irradiation enables a high throughput, but accordingly gives a greater damage to the semiconductor elements. Conversely, decreasing the RF power enables a reduction in the damage to the semiconductor elements, but accordingly lowers the throughput.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a chemical vapor deposition apparatus, a film forming method, and a method of manufacturing a semiconductor device which are capable of reducing the mixture of carbon and hydrocarbon into a TiN film in a MOCVD method.

The inventor of the present application has reached the following various aspects of the invention after repeated studious studies with the intention of solving the aforesaid problems.

A chemical vapor deposition apparatus according to the present invention includes: a chamber; a susceptor provided in the chamber; and a supplier supplying source gas containing organic metal into the chamber. The chemical vapor deposition apparatus further includes: a heater heating the organic metal supplied by the supplier to decompose the organic metal; and a trapper trapping carbon and hydrocarbon produced by decomposition of the organic metal before the organic metal reaches the susceptor.

In a method of manufacturing a semiconductor device according to the present invention, a base material is placed on the susceptor of the chemical vapor deposition apparatus described above, and thereafter, a film is grown on the base material by chemical vapor deposition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be concretely described with reference to the attached drawings.FIG. 1is a schematic view depicting a structure of a chemical vapor deposition apparatus (CVD apparatus) according to an embodiment of the present invention.

In this embodiment, as depicted inFIG. 1, a showerhead3emitting source gas containing organic metal is provided in an upper part of a chamber1. Examples of the organic metal are tetrakis (dimethylamino)titanium (TDMAT: Ti[N(CH3)2]4) and tetrakis (diethylamino)titanium (TDEAT: Ti[N(C2H5)2]4), but the organic metal is not limited to these. Further, carrier gas such as nitrogen gas, helium gas, and argon gas may be emitted from the showerhead3. Further, the source gas may contain ammonia for supplying nitrogen atoms.

Further, a stage (susceptor)4on which a base material10such as a semiconductor substrate is placed is provided in a lower part of the chamber1. As the base material10, used is, for example, a silicon substrate, a compound semiconductor substrate, and any of these substrates having an insulating film and/or an insulating film and so on formed thereon. Further, between the showerhead3and the stage4, a trapping member5trapping carbon atoms and hydrocarbon molecules is installed. The trapping member5contains, for example, a Pt group element such as Pt, Ru, Rh, Pd, OS, and Ir. Further, a heater2heating a space between the showerhead3and the trapping member5is provided in the chamber1.

Next, a description will be given of a method of forming a TiN film on the base material10by a MOCVD method with using the CVD apparatus as structured above.

First, the base material10is placed on the stage4. Next, the space between the showerhead3and the trapping member5is heated by the heater2to a temperature at which TDMAT is thermally decomposed (about 150° C.), or higher. Next, the source gas containing TDMAT and the carrier gas are emitted from the showerhead3into the chamber1. As a result, TDMAT emitted into the chamber1is thermally decomposed by the heater2into TiN, carbon (C), and hydrocarbon (CHx) in the space between the showerhead3and the trapping member5. Then, the TiN, carbon, and hydrocarbon move toward the base material10. Here, the trapping member5is installed in a movement route to the base material10. Therefore, the carbon and hydrocarbon are trapped by the trapping member5. On the other hand, the TiN passes through the trapping member5without being trapped to reach the base material10. As a result, a TiN film containing neither carbon nor hydrocarbon grows on a surface of the base material10.

As described above, according to the present embodiment, it is possible to grow, on the base material10, the TiN film containing neither carbon nor hydrocarbon. This eliminates a need for plasma processing for removing the carbon and hydrocarbon from the TiN film after the formation of the TiN film. Therefore, even when the TiN film needs to have a large thickness, there is no need to grow the TiN film in a plurality of divided processes. This greatly reduces the necessary number of processes and process time, enabling an improvement in throughput. Further, it is possible to prevent damages to semiconductor elements and the like accompanying the plasma processing. Further, no facility for the plasma processing is necessary, which simplifies the whole structure of the CVD apparatus.

Incidentally, in forming the TiN film, it is preferable to make the source gas contain a substance containing nitrogen atoms, such as ammonia. This is because, when the source gas contains no substance containing nitrogen atoms besides TDMAT or the like, a Ti film may be formed due to lack of nitrogen atoms or a TiN film containing excessive Ti may be formed. Conversely, in order to form a Ti film, source gas containing only TDMAT may be used.

Further, for forming the TiN film or the Ti film, the base material10need not be heated. A conventional CVD apparatus does not include what corresponds to the heater2, and thus, on the surface of the base material10, TDMAT and so on need to be thermally decomposed by heating the base material10up to an about 400° C. temperature, but in the present embodiment, the thermal decomposition on the surface of the base material10is not necessary. Conventionally, heating a base material including Al wiring up to a temperature higher than 400° C. has been avoided, which limits the kinds of usable organic metal. In the present embodiment, on the other hand, since the organic metal is thermally decomposed by the heating by the heater2, there is no need to heat the base material, and organic metal thermally decomposed at high temperatures is also usable.

The temperature of the space between the showerhead3and the trapping member5may be any provided that it is a temperature at which organic metal such as TDMAT is thermally decomposed, or higher, and too high a temperature only results in a greater load to the heater2. Therefore, the temperature of this space is preferably about 150° C. to 800° C.

Next, a description will be given of a method of manufacturing a semiconductor device with using the CVD apparatus described above.FIG. 2AtoFIG. 2Gare cross-sectional views depicting the method of manufacturing a semiconductor device in order of processes.

First, as depicted inFIG. 2A, an element isolation insulating film102is formed on a surface of a semiconductor substrate101by a STI (shallow trench isolation) method. Incidentally, the element isolation insulating film102may be formed by a LOCOS (local oxidation of silicon) method or the like. Next, in an element region defined by the element isolation insulating film102, a field-effect transistor is formed. In forming the field-effect transistor, a gate insulating film103and a gate electrode104are first formed. Next, low-concentration impurity diffused layers106, a sidewall insulating film105, and high-concentration impurity diffused layers107are sequentially formed.

Thereafter, as depicted inFIG. 2B, an interlayer insulating film108covering the field effect transistor is formed. Subsequently, contact holes109reaching the high-concentration impurity diffused layers107are formed in the interlayer insulating film108.

Next, as depicted inFIG. 2C, with using the CVD apparatus depicted inFIG. 1, a TiN film110as a barrier metal film is formed on bottom surfaces and side surfaces of the contact holes109and on a surface of the interlayer insulating film108by a MOCVD method. Incidentally, a Ti film may be formed before the formation of the TiN film110so that the barrier metal film may have two-layer structure.

Next, as depicted inFIG. 2D, a W film111filling the contact holes109are formed on the TiN film110. In forming the W film111, the CVD apparatus depicted inFIG. 1may be used.

Thereafter, as depicted inFIG. 2E, the W film111and the TiN film110are polished by a CMP (chemical mechanical polishing) method or the like until the surface of the interlayer insulating film108is exposed. As a result, contact plugs including the TiN film110and the W film111are left in the contact holes109.

Subsequently, as depicted inFIG. 2F, wirings connected to the contact plugs are formed. In forming the wirings, a TiN film112is formed with using the CVD apparatus depicted inFIG. 1, an Al film113is formed, and a TiN film114is formed with using the CVD apparatus depicted inFIG. 1, and these films are patterned. Incidentally, between the formation of the Al film113and the formation of the TiN film114, a Ti film may be formed with using the CVD apparatus depicted inFIG. 1. Further, in forming the Al film113, the CVD apparatus depicted inFIG. 1may be used.

As depicted inFIG. 2F, after the formation of the wirings, an interlayer insulating film115covering the wirings is formed. Next, via holes116reaching the wirings are formed in the interlayer insulating film115.

Next, in the same manner as the manner of forming the contact plugs including the TiN film110and the W film111, via plugs including the TiN film117and the W film118are formed in the via holes116.

Thereafter, upper wirings and so on are formed, whereby the semiconductor device is completed.

It should be noted that, though only TDMAT or TDEAT is named as the organic metal in the above description, other organic metal may be used. Further, the film to be formed is not limited to the TiN film or the Ti film.

Further, the application of the present invention is not limited to formation of a barrier metal film, and the present invention is also applicable to, for example, formation of a TiN film as a hard mask, formation of a TiN film or a Ti film as the whole or a part of an electrode, and the like.

Industrial Applicability

According to the present invention, since the organic metal is decomposed before reaching the susceptor and the carbon and hydrocarbon produced by the decomposition are trapped by the trapper, it is possible to prevent the carbon and hydrocarbon from mixing into the film formed on the base material. This can eliminate a need for plasma processing and the like for removing the carbon and hydrocarbon. Further, since the base material itself need not be heated, organic metal decomposed at relatively high temperatures is usable.