Method for manufacturing a semiconductor device, and said semiconductor device

A method for manufacturing a semiconductor device has forming a first metal wire in a groove formed in an insulating film on a semiconductor substrate, forming an interlayer dielectric on the insulating film and the first metal wire, forming a via hole by etching the interlayer dielectric, forming a first barrier metal on sidewalls of the via hole, forming an organic film in the via hole having the first barrier metal formed therein, etching the first barrier metal exposed by performing an etchback on the organic film to a predetermined position, forming a trench integrally with an upper portion of the via hole by etching the interlayer dielectric to a predetermined position, forming a second barrier metal on the first barrier metal and sidewalls of the trench in the via hole, after the organic film remaining in the via hole is removed, and forming a second metal wire in the via hole and the trench having the second barrier metal formed therein.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-123270, filed on May 8, 2007; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method for manufacturing a semiconductor device, and also relates to the semiconductor device. More particularly, the present invention relates to a method for manufacturing a semiconductor device having wires formed by a dual damascene process, and also relates to the semiconductor device.

As a process for forming wires of a semiconductor device, there has been a via-first dual damascene process that involves a low-k interlayer dielectric (a low dielectric constant film (a low-k film)). In this dual damascene process, a single damascene wire is formed on an insulating film, with a barrier metal being interposed between the single damascene wire and the insulating film. The low-k film such as a SiOC composition film is formed on the single damascene wire. A via hole is formed in the low-k film on the single damascene wire, and a wire groove is formed on the via hole. A wiring metal material is then provided to fill the via hole and the wire groove via a barrier metal. In the process of forming the via hole, the low-k film is etched by a resist processing technique and the reactive ion etching (RIE) technique, and the resist is removed by the Asher technique.

During the RIE process, however, the surface of the low-k film is exposed to a plasma atmosphere. As a result, the carbon (C), the methyl group (CH3), or the aryl group (CH substituent) in the low-k film are desorbed, and a SiO film is formed on the surface of the etched low-k film. Exposed to the air, the SiO film absorbs moisture to form a damaged layer (a SiOH layer) on the surface of the etched low-k film. The barrier metal reacts with the OH group in the damaged layer, to form an oxide film on the surface of the barrier metal. The oxide film lowers the reliability of the wires. During the Asher process, a damaged layer is also formed.

In a case where the damaged layer is removed by wet etching with the use of a chemical solution containing a HF-based substance, the low-k film is deformed by the amount corresponding to the removed damaged layer. As a result, a width of the trench (particularly, the via diameter) becomes greater, and hinders miniaturization of the semiconductor device.

As described above, by the conventional semiconductor device manufacturing process, it is difficult to increase a reliability of the wire and prevent an increase in a width of the trench during the dual damascene process (Japanese Patent Application Laid-Open No. 2006-5010).

SUMMARY OF THE INVENTION

According to the first aspect of the present invention, there is provided that a method for manufacturing a semiconductor device, comprising:

forming a first metal wire in a groove formed in an insulating film on a semiconductor substrate;

forming an interlayer dielectric on the insulating film and the first metal wire;

forming a via hole by etching the interlayer dielectric;

forming a first barrier metal on sidewalls of the via hole;

forming an organic film in the via hole having the first barrier metal formed therein;

etching the first barrier metal exposed by performing an etchback on the organic film to a predetermined position;

forming a trench integrally with an upper portion of the via hole by etching the interlayer dielectric to a predetermined position;

forming a second barrier metal on the first barrier metal and sidewalls of the trench in the via hole, after the organic film remaining in the via hole is removed; and

forming a second metal wire in the via hole and the trench having the second barrier metal formed therein.

According to the second aspect of the present invention, there is provided that a semiconductor device comprising:

an insulating film that is formed on a semiconductor substrate;

a first metal wire that is formed on a surface of the insulating film;

an interlayer dielectric that is formed on the insulating film and the first metal wire;

a second metal wire that is formed in the interlayer dielectric and on the first metal wire; and

first and second barrier metals that are formed between the second metal wire and the interlayer dielectric.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 1 to 6, a dual damascene process by which a via is formed on a semiconductor element placed on a silicon substrate is described.

FIG. 1is a cross-sectional view showing a process in the dual damascene process.

First, an insulating film101is formed on a contact hole (not shown) continuing to the semiconductor element. A trench pattern is then formed by a photolithography technique and an etching technique, so as to form a trench to bury a later described first metal wire (a Cu single damascene wire103).

A lower-layer wiring barrier metal102is formed inside the trench and on the entire surface of the insulating film101by a sputtering technique.

A wiring material (such as Cu) is formed on the entire surface of the lower-layer wiring barrier metal102by a sputtering technique or a plating technique, so as to fill the trench. The portions of the lower-layer wiring barrier metal102and the Cu existing outside the trench are removed by the chemical mechanical polishing (CMP) technique, so as to form the first metal wire (the Cu single damascene wire)103.

A diffusion preventing film (a SiCN film)104is then formed on the first metal wire (the Cu single damascene wire)103.

An interlayer dielectric (a low-k film)105such as a SiOC composition film is then formed on the diffusion preventing film (the SiCN film)104.

A TEOS film (a silicon insulating film)106is then formed as a low-k film capping material on the interlayer dielectric (the low-k film)105.

A first resist film107is then formed on the TEOS film (the silicon insulating film)106, and a via pattern is formed by a photolithography technique.

FIG. 2is a cross-sectional view showing the process following the process shown inFIG. 1in the dual damascene process.

After the via pattern is formed by a photolithography technique, etching is performed on the TEOS film106and the interlayer dielectric (the low-k film)105by RIE, so as to form a via hole. The first resist film107used as a mask is then removed by the Asher technique. During the RIE process, the interlayer dielectric (the low-k film)105is exposed to a plasma atmosphere, and a SiO layer is formed on the inner faces of the via hole. As the SiO layer absorbs moisture, a damaged layer (a SiOH layer)108is formed on the inner faces of the via hole. During the Asher process, the damaged layer (the SiOH layer)108on the surface of the interlayer dielectric (the low-k film)105is also formed.

Spin coating is then performed to form an organic film110that fills the via hole, and an inorganic film111is formed on the organic film110.

A second resist112is next formed on the inorganic film111, and a trench pattern is formed by a photolithography technique. At this point, the amine group (NH) generated from the surface of the diffusion preventing film (the SiCN film)104exposed by RIE forms skirt portions on the second resist112(see the portions indicated by the broken lines inFIG. 2). The amine group (NH) leaves unresolved portions in a photolithography process of an oxidation enhancing type.

FIG. 3is a cross-sectional view showing the process following the process shown inFIG. 2in the dual damascene process.

After the trench pattern is formed by a photolithography technique, etching is performed on the inorganic film111, the organic film110, the TEOS film (the silicon insulating film)106, and the interlayer dielectric (the low-k film)105by RIE. At the time of etching of the TEOS film (the silicon insulating film)106and the interlayer dielectric (low-k) film105, etching is also performed on the organic film110filling the via hole. Also, at the time of etching of the interlayer dielectric (the low-k film)105, half-etching which is stopped halfway is performed, and a trench for burying a later described second metal wire (a Cu dual damascene wire)115is formed. At this point, the damaged layer (the SiOH layer)108shown inFIG. 2in the interlayer dielectric (the low-k film)105is removed, but another damaged layer (a SiOH layer)108′ exposed to a plasma atmosphere and the air or the like is formed in the same manner as above.

FIG. 4is a cross-sectional view showing the process following the process shown inFIG. 3in the dual damascene process.

After the trench is formed, the remaining organic film110is removed by the Asher technique, and etching is performed on the diffusion preventing film (the SiCN film)104inside the via hole by RIE, with the TEOS film (the silicon insulating film)106being used as a mask. At this point, the first metal wire (the Cu single damascene wire)103below the via hole is exposed. The interlayer dielectric (the low-k film)105is exposed to a plasma atmosphere and the air or the like, and an additional SiO layer is formed on the surface of the interlayer dielectric (the low-k film)105inside the via hole and the trench. Particularly, since the inside of the via hole is exposed to a denser plasma atmosphere, the interlayer dielectric (the low-k) film)105is deformed dramatically at the upper corners of the via, and the formation of the SiO layer becomes more noticeable. The SiO layer at the upper corner portions of the via is exposed to the air, and absorbs moisture. As a result, a large damaged layer (a SiOH layer)108″ is formed.

FIG. 5is a cross-sectional view showing the process following the process shown inFIG. 4in the dual damascene process.

After etching is performed on the diffusion preventing film (the SiCN film)104, wet etching is performed with the use of a chemical solution containing a HF-based substance, so as to perform the postprocessing of the etching and clean the Cu surface of the first metal wire (the single damascene wire)103. Since the SiO layer and the damaged layers (SiOH layers)108,108′, and108″ formed on the surface of the interlayer dielectric (the low-k film)105inside the trench and the via hole do not have tolerance to a chemical solution containing a HF-based substance, those layers are removed by the wet etching. As a result, a width of the trench (particularly, the via diameter) becomes greater by the widths of the removed SiO layer and the removed damaged layers (SiOH layer)108,108′, and108″, and it becomes difficult to reduce the size of the semiconductor device. If the wet etching is performed with a chemical solution not containing a HF-based substance, or wet etching is not performed at all, the damaged layers (SiOH layers)108,108′, and108″ remain to lower the reliability of the wires of the semiconductor device.

FIG. 6is a cross-sectional view showing the process following the process shown inFIG. 5in the dual damascene process.

After the wet etching is performed, a first barrier metal109is formed on the entire surface including the inside of the via hole and the inside of the trench. If the damaged layers (SiOH layers)108,108′, and108″ remain, the OH group contained in the damaged layers (SiOH layers)108,108′, and108″ reacts with the material of the first barrier metal109during the high-temperature processing performed after the formation of the first barrier metal109. As a result, a barrier metal oxide film is formed to lower the reliability of the wires.

After a seed layer114is formed, a wiring material (such as Cu) is formed on the entire surface of the first barrier metal109by a sputtering technique or a plating technique, so as to fill the via hole and the trench. To prevent short-circuiting between the trench wires, the portions of the first barrier metal109and the seed layer114, and the Cu exiting outside the trench are removed by CMP. In this manner, a second metal wire (a Cu dual damascene wire)115is formed.

Next, an embodiment of the present invention is described, with reference to the accompanying drawings. It should be noted that the following embodiment is merely an example, and does not limit the scope of the present invention.

Referring to the accompanying drawings, Embodiment 1 of the present invention is described. In Embodiment 1 of the present invention, after a via is formed, a barrier metal is formed on the interlayer dielectric of the side walls of the via.

Referring toFIG. 1andFIGS. 7 to 12, the dual damascene process of Embodiment 1 of the present invention is described.

First, as in the process shown inFIG. 1, an insulating film101is formed on a contact hole continuing to a semiconductor element, a lower-layer wiring barrier metal102, a first metal wire (a Cu single damascene wire)103, a diffusion preventing film (a SiCN film)104, an interlayer dielectric (a low-k film)105, a TEOS film (a silicon insulating film)106, and s first resist107are formed. A via pattern is then formed by a photolithography technique.

The interlayer dielectric (the low-k film)105may be a methyl-silsesquioxane (a SiOC film), an insulating film that has Si as its skeleton and is terminated with a methyl group (CH3), or an insulating film that has Si as its skeleton and is terminated with an aryl group (CH substituent group), for example. When such an insulating film is exposed to a plasma atmosphere, the methyl group (CH3) or the aryl group (CH substituent group) is detached and is bonded with the oxygen in the air, to form a SiO layer. The SiO layer then absorbs moisture to form a damaged layer (s SiOH layer).

FIG. 7is a cross-sectional view showing the process following the process shown inFIG. 1in the dual damascene process of Embodiment 1 of the present invention.

After a via pattern is formed by a photolithography technique, etching is performed thoroughly on the TEOS film (the silicon insulating film)106, the interlayer dielectric (the low-k film)105, and the diffusion preventing film (the SiCN film)104by RIE (so as to expose the first metal wire (the Cu single damascene wire)103). In this manner a via hole is formed, and the first resist107used as a mask is removed by the Asher technique. At this point, the interlayer dielectric (the low-k film)105is exposed to a plasma atmosphere by RIE and the Asher technique, so as to form a SiO layer on the inner faces of the via hole. The SiO layer then absorbs moisture to form a damaged layer (a SiOH layer)108.

FIG. 8is a cross-sectional view showing the process following the process shown inFIG. 7in the dual damascene process of Embodiment 1 of the present invention.

After the first resist107is removed, wet etching is performed with the use of a chemical solution containing a HF-based substance, so as to remove the damaged layer (the SiOH layer)108.

A first barrier metal109is then formed on the entire surface, including the inside which is sidewalls and a bottom surface of the via hole. The material of the first barrier metal109is a Ti-based film, in view of easiness of processing.

Spin coating is then performed to form an organic film110that fills the via hole, and an inorganic film111is formed on the organic film110.

A second resist112is next formed, and a trench pattern is formed by a photolithography technique. At this point, the first barrier metal109serves to shield the amine group (NH) generated from the surface of the diffusion preventing film (the SiCN film)104. Accordingly, the above described skirt portions and the unresolved portions are not formed, and a photolithography process of an oxidation enhancing type can be properly carried out.

FIG. 9is a cross-sectional view showing the process following the process shown inFIG. 8in the dual damascene process of Embodiment 1 of the present invention.

After the trench pattern is formed by a photolithography technique, etching is performed on the inorganic film111and the organic film110by RIE. When the etching is performed on the organic film110filling the via hole, selective etching is performed on the first barrier metal109, so as to form a recess that reaches a predetermined height of the interlayer dielectric (the low-k film)105(so as to leave part of the organic film110in the via hole).

FIG. 10is a cross-sectional view showing the process following the process shown inFIG. 9in the dual damascene process of Embodiment 1 of the present invention.

After the recess is formed, selective and isotropic etching is performed thoroughly on the first barrier metal109by RIE or chemical dry etching (CDE), with respect to the organic film110remaining in the via hole. Exposed to a plasma atmosphere by RIE, a SiO layer is formed on the inner faces of the via hole, and the SiO layer absorbs moisture to form another damaged layer (a SiOH layer)108′.

FIG. 11is a cross-sectional view showing the process following the process shown inFIG. 10in the dual damascene process of Embodiment 1 of the present invention.

After the first barrier metal109is partially etched, half-etching is performed on the TEOS film (the silicon insulating film)106, the interlayer dielectric (the low-k film)105, and the damaged layer (the SiOH layer)108′ to a predetermined height (to a higher position than the first barrier metal109and the organic film110remaining in the via hole) by RIE, with the inorganic film111and the organic film110being used as masks. In this manner, another damaged layer (a SiOH layer)108″ is formed on the sidewalls of the interlayer dielectric (the low-k film)105as described above.

At the time of the etching of the interlayer dielectric (the low-k film)105, half-etching is performed so that the etching is stopped at a higher position than the first barrier metal109remaining in the via hole. At this point, the first barrier metal109that is not etched serves as a shield, and the interlayer dielectric (the low-k film)105is not exposed to a plasma atmosphere and the air or the like. Accordingly, the via upper corners of the interlayer dielectric (the low-k film)105are not dramatically deformed, and the formation of a new damaged layer (a SiOH layer) on the side faces of the interlayer dielectric105is prevented. Thus, adverse influence on the Cu burying characteristics and the reliability of the wires can be reduced.

FIG. 12is a cross-sectional view showing the process following the process shown inFIG. 11in the dual damascene process of Embodiment 1 of the present invention.

After etching is performed on the TEOS film (the silicon insulating film)106, the interlayer dielectric (the low-k film)105, and the damaged layer (the SiOH layer)108′, etching is performed on the first barrier metal109. To remove the damaged layer (the SiOH layer)108″, wet etching is performed with the use of a chemical solution containing a HF-based substance.

The remaining organic film110is then removed by the Asher technique. In the dual damascene process of Embodiment 1 of the present invention, the first barrier metal109serves as a shield, and the interlayer dielectric (the low-k film)105is not exposed to a plasma atmosphere and the air or the like. Accordingly, a new damaged layer (a SiOH layer) is not formed on the sidewalls of the via hole during the Asher process. Also, in the dual damascene process of Embodiment 1 of the present invention, the diffusion preventing film (the SiCN film)104does not need etching, and the shapes of the via upper corners can be maintained as they are formed when the via hole is processed.

A second barrier metal113is formed on the entire surface, including the inside of the via hole and the inside of the trench. In a conventional dual damascene process, it becomes more difficult to form a barrier metal uniformly on a surface including the inside of the via hole in a dual damascene structure having a complicated shape, as the structure becomes smaller. In the dual damascene process of Embodiment 1 of the present invention, however, the first barrier metal109already exists inside the via hole at this point. Therefore, it is not necessary to uniformly form the second barrier metal113, and the formation of the second barrier metal113is easier.

After a seed layer114is formed on the entire surface including the upper face of the second barrier metal113, Cu is formed on the entire surface of the seed layer114by a sputtering technique or a plating technique, so as to fill the via hole and the trench. To prevent short-circuiting between the trench wires, the portions of the second barrier metal113, the seed layer114, and the Cu existing outside the trench are removed by CMP, so as to form a second metal wire (a Cu dual damascene wire)115.

FIG. 13is a schematic cross-sectional view of a semiconductor device that is manufactured by the dual damascene process of Embodiment 1 of the present invention.

In this semiconductor device, the first metal wire (the Cu single damascene wire)103connected to the second metal wire (the Cu dual damascene wire)115is located at a distance of approximately 100 nm from an unconnected wire103′ that is not connected to the second metal wire (the Cu dual damascene wire)115. The width of each of the first metal wire (the Cu single damascene wire)103and the unconnected wire103′ is approximately 100 nm.

In a case where the damaged layers (SiOH layers) are removed to increase a reliability of the wire as described above, the via diameter becomes larger, and the distance between the second metal wire (the Cu dual damascene wire)115and the unconnected wire103′ becomes shorter. For example, in a case where the via diameter increases 70 nm, the distance between the second metal wire (the Cu dual damascene wire)115and the unconnected wire103′ becomes 30 nm.

To avoid current leakage, a certain distance or longer needs to be maintained between the second metal wire (the Cu dual damascene wire)115and the unconnected wire103′. On the other hands, to reduce the size of the semiconductor device, the distance between the first metal wire (the Cu single damascene wire)103and the unconnected wire103′ needs to be made shorter. Accordingly, to manufacture a small-sized semiconductor device having high reliability, it is necessary not only to increase the processing precision in the dual damascene process, but also to prevent an increase in the via diameter.

As shown inFIG. 13, the semiconductor device in accordance with Embodiment 1 of the present invention includes the insulating film101formed on a semiconductor substrate, the first metal wire103formed in the insulating film101, the interlayer dielectric (the low-k film)105formed on the insulating film101, the second metal wire115formed in the interlayer dielectric (the low-k film)105, the first barrier metal109formed on side walls and a bottom surface of the via hole to be located between the second metal wire115and the interlayer dielectric (the low-k film)105, and the second barrier metal113formed on the first barrier metal109and side walls of the trench in the via hole.

The seed layer114is formed between the second metal wire115and the first and second barrier metals109and113. The first barrier metal109is formed below the second metal wire115, and is in contact with the first metal wire103. The second barrier metal113is located between the seed layer114and the interlayer dielectric (the low-k film)113.

In Embodiment 1 of the present invention, the first barrier metal109and the second barrier metal113are formed on the sidewalls of the interlayer dielectric (the low-k film)105. Accordingly, plasma damage to the interlayer dielectric (the low-k film)105due to RIE or the Asher process can be prevented, and a damaged layer (a SiOH layer) is not formed on the sidewalls of the interlayer dielectric (the low-k film)105. As a result, an increase in the via diameter can be reduced, and a reliability of the wire can be increased. Particularly, as the dielectric constant of the interlayer dielectric (the low-k film)105becomes smaller, the effects of Embodiment 1 of the present invention become more remarkable.

Also, since the first barrier metal109is formed on the entire surface including the inside of the via hole in Embodiment 1 of the present invention, the amine group (NH) generated from the diffusion preventing film (the SiCN film)104and the interlayer dielectric (the low-k film)105can be restrained, and a photolithography process of an oxidation enhancing type can be properly carried out.

Also, since the first barrier metal109is formed on the surface of the first metal wire (the Cu single damascene wire)103in Embodiment 1 of the present invention, a via hole can be formed to expose the first metal wire (the Cu single damascene wire)103, and the formation of the via hole is easier.