Patent Application
20070018255
The present invention relates to a semiconductor device and a method for fabricating the same, more specifically, a semiconductor device and a method for fabricating the same in which silicidation with nickel is performed.
As a technique of making the gate electrode and the source/drain diffused layers low resistive, the so-called salicide (self-aligned silicide) process that metal silicide film is formed on the surfaces of the gate electrode and the source/drain diffused layers by self-alignment is known. As the metal material reacted with silicon in the salicide process, cobalt (Co) is widely used (see, e.g., Patent Reference 1).
On the other hand, as the semiconductor device is increasingly integrated, the structure of the semiconductor device is rapidly increasingly fined. Specifically, the junction depth of the source/drain diffused layer is as small as below 80 nm excluding 80 nm. The film thickness of the metal silicide film formed on the source/drain diffused layer is as small as below 20 nm excluding 20 nm. The gate length is as small as below 50 nm excluding 50 nm.
While the structure of the semiconductor device is being increasingly fined, the phenomenon that the scatter of the resistance of the gate electrode abruptly increases when Co is used to form CoSi2 film on the gate electrode is observed in fabricating a semiconductor device having the gate electrode with a gate length below 40 nm including 40 nm.
In contrast to such CoSi2, nickel silicide is much noted because of the advantage that the resistance of the gate electrode is stable even when the gate length is below 40 nm excluding 40 nm.
The following references disclose the background art of the present invention.
[Patent Reference 1]
Japanese Patent Application Unexamined Publication No. Hei 9-251967 (1997)
[Patent Reference 2]
Specification of U.S. Pat. No. 6,621,131
However, when Ni film is simply used for the silicidation, the roughness in the interface between the silicon layer and the silicide film becomes large, and often the scatter of the sheet resistance of the source/drain diffused layer is increased, and the junction leak current is increased.
An object of the present invention is to provide a semiconductor device which can suppress the scatter of the sheet resistance of the source/drain diffused layers and the junction leak current, and a method for fabricating the same.
According to one aspect of the present invention, there is provided a semiconductor device comprising: a gate electrode formed on a semiconductor substrate; a source/drain diffused layer formed in the semiconductor substrate on both sides of the gate electrode; and a silicide film formed on the source/drain diffused layer, the silicide film being formed of nickel monosilicide, and a film thickness of the silicide film being below 20 nm including 20 nm.
According to another aspect of the present invention, there is provided a semiconductor device comprising: a gate electrode formed on a semiconductor substrate; a source/drain diffused layer formed in the semiconductor substrate on both sides of the gate electrode; an Si1-xGex film which is buried in the source/drain diffused layer and whose composition ratio x is 0<x<1; and a silicide film formed on the Si1-xGex film, the silicide film being formed of NiSi1-xGex whose composition ratio x is 0<x<1, and a film thickness of the silicide film being below 20 nm including 20 nm.
According to further another aspect of the present invention, there is provided a semiconductor device comprising: a gate electrode formed on a semiconductor substrate; a source/drain diffused layer formed in the semiconductor substrate on both sides of the gate electrode, an Si1-x-yGexCy film which is buried in the source/drain diffused layer and whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0; and a silicide film formed on the Si1-x-yGexCy film, the silicide film being formed of NiSi1-x-yGexCy whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0, and a film thickness of the silicide film being below 20 nm including 20 nm.
According to further another aspect of the present invention, there is provided a method for fabricating a semiconductor device comprising the steps of: forming a gate electrode on a semiconductor substrate; forming a source/drain diffused layer in the semiconductor substrate on both sides of the gate electrode; forming a nickel film on the source/drain diffused layer; performing a first thermal processing to react a lower part of the nickel film and an upper part of the source/drain diffused layer with each other to form a nickel silicide film on the source/drain diffused layer; etching off selectively a part of the nickel film, which has not reacted; and performing a second thermal processing to further react the nickel silicide film and an upper part of the source/drain diffused layer with each other.
According to further another aspect of the present invention, there is provided a method for fabricating a semiconductor device comprising the steps of: forming a gate electrode on a semiconductor substrate; forming a source/drain diffused layer in the semiconductor substrate on both sides of the gate electrode; burying Si1-xGex film whose composition ratio x is 0<x<1 in the source/drain diffused layer; forming a nickel film on the Si1-xGex film; performing a first thermal processing to react a lower part of the nickel film and an upper part of the Si1-xGex film to form a nickel silicide film on the Si1-xGex film; etching off selectively a part of the nickel film, which has not reacted; and performing a second thermal processing to further react the nickel silicide film and an upper part of the Si1-xGex film with each other.
According to further another aspect of the present invention, there is provided a method for fabricating a semiconductor device comprising the steps of: forming a gate electrode on a semiconductor substrate; forming a source/drain diffused layer in the semiconductor substrate on both sides of the gate electrode; burying an Si1-x-yGexCy film whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0 in the source/drain diffused layer; forming a nickel film on the Si1-x-yGexCy film; performing a first thermal processing to react a lower part of the nickel film and an upper part of the Si1-x-yGexCy film with each other to form a nickel silicide film on the Si1-x-yGexCy film; etching off selectively a part of the nickel film, which has not reacted; and performing a second thermal processing to further react the nickel silicide film and an upper part of the Si1-x-yGexCy film with each other.
According to the present invention, by the first thermal processing, a lower part of a relatively thick nickel film and an upper part of a silicon substrate are reacted with each other, whereby by the first thermal processing, an Ni2Si film can be formed while the formation of NiSi2 crystals is being suppressed. Then, in the present invention, after the part of the nickel film, which has not reacted with Si, is selectively etched off, by the second thermal processing, the Ni2Si film and an upper part of the silicon substrate are reacted with each other to form an NiSi film, whereby the NiSi film is prevented from being formed too thick. Furthermore, according to the present invention, the conditions for the first and the second thermal processing are suitably set, whereby the film thickness of the NiSi film can be controlled. Thus, according to the present invention, the NiSi film of good quality and low resistance can be formed in a required film thickness on the silicon substrate while the formation of NiSi2 film of high resistance is being suppressed, and the roughness in the interface between the silicon substrate and the NiSi film can be made small. Thus, when the surface of the gate electrode and the surface of the source/drain diffused layer are silicided, the scatter of the sheet resistance can be suppressed. The junction leak current can be suppressed.
According to the present invention, by the first thermal processing, a lower part of a relatively thick nickel film and an upper part of the Si1-xGex film are reacted with each other, whereby an Ni2Si1-xGex film can be formed while the formation of Ni(Si1-xGex)2 crystals is being suppressed. Then, in the present invention, after the part of the nickel film, which has not reacted with Si1-xGex, is selectively etched off, by the second thermal processing, the Ni2Si1-xGex film and an upper part of the Si1-xGex film are reacted with each other to form an NiSi1-xGex film, whereby the NiSi1-xGex film is prevented from being formed too thick. Furthermore, according to the present invention, the conditions for the first and the second thermal processing are suitably set, whereby the film thickness of the NiSi1-xGex film can be controlled. Thus, according to the present invention, the NiSi1-xGex film of low resistance and good quality can be formed in a required film thickness on the Si1-xGex film while the formation of Ni(Si1-xGex)2 film of high resistance is being suppressed. The roughness in the interface between the Si1-xGex film and the NiSi1-xGex film can be made small. Thus, when the surface of the gate electrode having the Si1-xGex film on the top and the surface of the Si1-xGex film buried in the source/drain diffused layer are silicided, the scatter of the sheet resistance can be suppressed. The junction leak current can be suppressed. Besides, according to the present invention, compressive strain is exerted to the channel layer of the PMOS transistor by the Si1-xGex film buried in the source/drain diffused layer of the PMOS transistor, whereby the operation speed of the PMOS transistor can be improved.
According to the present embodiment, by the first thermal processing, a lower part of a relatively thick nickel film and an upper part of the Si1-x-yGexCy film are reacted with each other, whereby by the first thermal processing, an Ni2Si1-x-yGexCy film can be formed while the formation of Ni(Si1-x-yGexCy)2 crystals is being suppressed. Then, in the present invention, after the part of the nickel film, which has not reacted with Si1-x-yGexCy, is selectively etched off, by the second thermal processing, the Ni2Si1-x-yGexCy film and an upper part of the Si1-x-yGexCy film are reacted with each other to form an NiSi1-x-yGexCy film, whereby the NiSi1-x-yGexCy film is prevented from being formed too thick. Furthermore, the conditions for the first and the second thermal processing are suitably set, whereby the film thickness of the NiSi1-x-yGexCy film can be controlled. Thus, according to the present invention, the NiSi1-x-yGexCy film of low resistance and good quality can be formed in a required film thickness on the Si1-x-yGexCy film while the formation of Ni(Si1-x-yGexCy)2 film of high resistance is being suppressed. The roughness in the interface between the Si1-x-yGexCy film and the NiSi1-x-yGexCy film can be made small. Thus, when the surface of the gate electrode having the Si1-x-yGexCy film on the top and the surface of the Si1-x-yGexCy film buried in the source/drain diffused layer are silicided, the scatter of the sheet resistance can be suppressed. The junction leak current can be suppressed. Furthermore, according to the present invention, tensile strain is exerted to the channel layer of the NMOS transistor by the Si1-x-yGexCy film buried in the source/drain diffused layer of the NMOS transistor, whereby the operation speed of the NMOS transistor can be improved.
[Principle of the Present Invention]
First, the principle of the present invention will be explained with reference to
As the reaction model of the silicidation process for forming nickel silicide of a silicon substrate and Ni film, different reaction models for the Ni film of different film thicknesses have so far reported. In the specification of the present application, “nickel silicide” widely means compounds of nickel and silicon, and to make a composition of nickel silicide explicit, “dinickel silicide (Ni2Si)”, “nickel monosilicide (NiSi)” or “nickel disilicide (NiSi2)” is discriminably used.
First, for the silicidation process in which a sufficiently thick Ni film of an about 200 nm-thickness is formed on a silicon substrate, and thermal processing is performed, the reaction model as described below has been reported (refer to F. d'Heurle, et al., J. Appl. Phys., vol. 55, pp. 4208-4218 (1984)).
When the thermal processing is performed with a nickel (Ni) film 12 of an about 200 nm-thickness formed on a silicon substrate 10 with face orientation (111) or (100) (see
Then, when the thermal processing is set on, the Ni2Si film 14 grows as illustrated in
Then, when the thermal processing is further set on, as illustrated in
Then, when the thermal processing is further set on, as illustrated in
As described above, in the silicidation process using a sufficiently thick Ni film of an about 200 nm-thickness, the reaction advances in the order of Ni2Si and NiSi.
On the other hand, the result of the section observation with a transmission electron microscope made for the case that a thin Ni film of a 12 nm-thickness is formed on a silicon substrate, and the thermal processing was performed has been reported (V. Teodorescu, et al., J. Appl. Phys., vol. 90, pp. 167-174 (2001)). The reaction model obtained by the observation with a transmission electron microscope is as follows.
When the thermal processing is performed with an Ni film 12 of an about 12 nm-thickness formed on a silicon substrate 10 with a face orientation (001) (see
When the thermal processing is further set on, as illustrated in
Then, when the thermal processing is further set on, as illustrated in
As described above, in the silicidation process using a relatively thin Ni film of an about 12 nm-thickness, the reaction advances in the order of NiSi2 and NiSi, and NiSi2 crystals are formed ununiform below the NiSi film.
As described above, depending on film thicknesses of the Ni film formed on the silicon substrate, the reaction process of the silicidation differs.
When the thermal processing is performed with a relatively thick Ni film of an about 200 nm-thickness, as described above, the reaction advances in the order of Ni2Si and NiSi, and NiSi film can be formed uniform. The roughness in the interface between the silicon substrate and the NiSi film becomes small. However, as the semiconductor device is increasingly fined, the height of the gate electrode is below 100 nm including 100 nm, and the junction depth of the source/drain diffused layer is small. When the source/drain diffused layer of such small junction depth is silicided with a thick Ni film, an NiSi film the film thickness of which is too large relative to the junction depth is formed on the source/drain diffused layer. With an NiSi film which is too thick relative to a junction depth formed on the source/drain diffused layer, the junction leak current is increased.
On the other hand, when the thermal processing is performed with a relatively thin Ni film of an about 12 nm-thickness, as described above, an NiSi film is formed, and NiSi2 crystals are also formed ununiform below the NiSi film. Here, the specific resistance of the NiSi is 14 μΩ·cm, and the specific resistance of the NiSi2 is 34 μΩ·cm which is more than twice the specific resistance of the NiSi.
The NiSi2 crystals of high resistance thus formed ununiform increase the roughness in the interface between the silicon substrate and the NiSi film, which is a cause for the scatter increase of the sheet resistance and is also a cause for the junction leak current increase.
Here, the source/drain diffused layer 28 has the junction depth smaller at a part near the end of the sidewall insulation film 26. Accordingly, as illustrated in
In the semiconductor device of the 90 nm-node technology, the junction depth of the source/drain diffused layer is below about 80 nm including 80 nm. Accordingly, the film thickness of a metal silicide film to be formed on the source/drain diffused layer as the source/drain electrode must be below 20 nm including 20 nm which can sufficiently suppress the generation of the junction leakage. Accordingly, the film thickness of the Ni film to be used in the silicidation of the source/drain diffused layer is preferably below about 13 nm including 13 nm. On the other hand, as described above, to form the Ni film thin forms the NiSi2 crystals ununiform, which is a cause for the scatter of the sheet resistance and junction leak current. As described above, in siliciding a fine MOS transistor with Ni film, the conventional method does not allow the Ni film to be formed thick, and it will be difficult for the conventional method to prevent the formation of the NiSi2 crystals which cause the deterioration of the transistor characteristics.
To specify the film thickness of the Ni film which permits the silicidation while suppressing the formation of the NiSi2 crystals, the inventor of the present application made the experiment of measuring the sheet resistance of the source/drain diffused layer silicided with Ni film of different thicknesses. In the experiment, the surface of a 0.14 μm-width source/drain diffused layer doped with boron ions was silicided with Ni film of a 10 nm-thickness, a 12 nm-thickness, a 15 nm-thickness, 17 nm-thickness and a 20 nm-thickness. The sheet resistance was measured on a plurality of samples of the Ni film of each film thickness, and the cumulative probabilities of the samples were plotted.
As evident based on the experiment result shown in
On the other hand, when the film thickness of the Ni film is below 17 nm excluding 17 nm, the scatter of the sheet resistance of the silicided source/drain diffused layer is conspicuous. Based on this result, when the film thickness of the Ni film is below 17 nm excluding 17 nm, it can be seen that the NiSi2 crystals are formed. That is, in this case, the silicidation will take place in accordance with the reaction model illustrated in
The film thickness of the NiSi film formed from the Ni film of a film thickness of above 20 nm including 20 nm becomes above 30 nm including 30 nm. When the surface of the gate electrode and the surface of the source/drain diffused layer are simply silicided with Ni film of a thickness of above 20 nm including 20 nm, the formation of the NiSi2 crystals is suppressed, but there is a risk that the junction leak current will be increased.
The inventor of the present application made earnest studies and have obtained an idea that the following method will be able to form the NiSi film in a required film thickness while suppressing the formation of the NiSi2 crystals of high resistance. The silicidation process of the present invention will be explained with reference to
First, as illustrated in
Next, as the first thermal processing, thermal processing is performed by, e.g., RTA (Rapid Thermal Annealing) at 270° C. and for 30 seconds. Thus, as illustrated in
Then, as illustrated in
Then, as the second thermal processing, thermal processing is performed by, e.g., RTA at 500° C. for 30 seconds. Thus, as illustrated in
As described above, in the silicidation of the present invention, the lower part of the relatively thick Ni film 12 and the upper part of the silicon substrate 10 are reacted with each other by the first thermal processing. The relatively thick Ni film 12 is used, whereby by the first thermal processing, the Ni2Si film 14 can be formed while the formation of the NiSi2 crystals is being suppressed. After the part of the Ni film 12 which has not reacted with the Si is selectively removed by etching, the Ni2Si film 14 and the upper part of the silicon substrate 10 are reacted with each other to form the NiSi film 16, whereby the NiSi film 16 is prevented from being formed too thick. The film thickness of the NiSi film can be controlled by suitably setting conditions such as the thermal processing temperatures and the thermal processing periods of time of the first thermal processing and the second thermal processing, etc.
Thus, the NiSi film 16 of low resistance and good quality can be formed in a required film thickness on the silicon substrate 10 while the formation of the NiSi2 film of high resistance is being suppressed, and the roughness in the interface between the silicon substrate 10 and the NiSi film 16 can be made small. Thus, when the surface of the gate electrode and the surface of the source/drain diffused layer are silicided, the scatter of the sheet resistance can be suppressed. The junction leak current can be suppressed.
To form the Ni2Si film by the first thermal processing while suppressing the formation of the NiSi2 film, it is preferable to set the film thickness of the Ni film at above 17 nm including 17 nm. The reason for this is as follows.
As shown in the graph of
On the other hand, with about 17 nm of the film thickness of the Ni film as the boundary, when the film thickness of the Ni film is larger than the boundary film thickness, the system formed of the silicon substrate and the Ni2Si film will have a smaller Gibbs free energy than the system formed of the silicon substrate and the NiSi2 film, and in this case, the Ni2Si film will be formed stably. That is, the film thickness of the Ni film is set at above 17 nm including 17 nm, whereby the formation of the NiSi2 film will be able to be sufficiently suppressed.
As described above, the film thickness of the Ni film is set at above 17 nm including 17 nm, more preferably above 20 nm including 20 nm, whereby by the first thermal processing, the Ni2Si film will be able to be formed while suppressing the formation of the NiSi2 film. This can be endorsed by the result of measuring the sheet resistance of the source/drain diffused layer shown in
The semiconductor device and the method for fabricating the same according to a first embodiment of the present invention will be explained with reference to FIGS. 7 to 22.
First, the structure of the semiconductor device according to the present embodiment will be explained with reference to
A device isolation region 46 for defining a device region is formed in a silicon substrate 34. A well (not illustrated) is formed in the silicon substrate 34 with the device isolation region 46 formed in.
On the silicon substrate 34 with the well formed in, a gate electrode 54 of polysilicon film is formed with a gate insulation film 52 of a silicon oxide film formed therebetween. A nickel silicide film 72a of NiSi alone is formed on the gate electrode 54. That is, the nickel silicide film 72a is formed of only nickel silicide of NiSi phase alone. The film thickness of the nickel silicide film 72a is, e.g., below 20 nm including 20 nm.
A sidewall insulation film 60 is formed on the side wall of the gate electrode 54 with the nickel silicide film 72a formed on.
A channel doped layer 50 is formed in the silicon substrate 34 below the gate electrode 54. In the silicon substrate 34 on both sides of the gate electrode 54, source/drain diffused layers 64 formed of a shallow impurity diffused region 58 forming the extension region of the extension source/drain structure and a deep impurity diffused region 62 are formed. On the source/drain diffused layers 64, nickel silicide films 72b of NiSi alone are formed. That is, the nickel silicide film 72b is formed of only nickel silicide of NiSi phase alone. The film thickness of the nickel silicide film 72b is, e.g., below 20 nm including 20 nm.
Thus, a MOS transistor including the gate electrode 54 and the source/drain diffused layers 64 is formed on the silicon substrate 34.
On the silicon substrate 34 with the MOS transistor formed on, a silicon nitride film 74 is formed. On the silicon nitride film 74, a silicon oxide film 76 is formed.
In the silicon oxide film 76 and the silicon nitride film 74, a contact hole 78a is formed down to the nickel silicide film 72a on the gate electrode 54. In the silicon oxide film 76 and the silicon nitride film 74, contact holes 78b are formed down to the nickel silicide films 72b on the source/drain diffused layers 64.
In the contact holes 78a, 78b, contact plugs 84a, 84b of a barrier metal 80 and a tungsten film 82 are respectively buried.
An inter-layer insulation film 86 is formed on the silicon oxide film 76 with the contact plugs 84a, 84b buried in.
Thus, the semiconductor device according to the present embodiment is constituted.
The semiconductor device according to the present embodiment is characterized mainly in that the nickel silicide films 72a, 72b formed respectively on the gate electrode 54 and the source/drain diffused layers 64 are formed of only nickel silicide of NiSi phase alone.
That is, in the semiconductor device according to the present embodiment, no NiSi2 crystals are formed in the nickel silicide films 72a, 72b. No NiSi2 crystals are formed either in the interface between the nickel silicide film 72a and the gate electrode 54 and in the interfaces between the nickel silicide films 72b and the silicon substrate 34.
As described above, the nickel silicide films 72a, 72b are formed of only nickel silicide of NiSi phase alone, whereby the roughness in the interface between the NiSi film 72a and the gate electrode 54 and in the interfaces between the NiSi films 72b and the source/drain diffused layers 64 can be made small, and the scatter of the sheet resistances of the surface of the gate electrode 54 and the surfaces of the source/drain diffused layers 64 can be suppressed.
The film thickness of the nickel silicide film 72b is as thin as, e.g., below 20 nm including 20 nm, and furthermore, the NiSi2 crystals, which are a cause for generating the junction leakage are not formed down to the vicinity of the junctions of the source/drain diffused layers 64, whereby even when the junction depths of the source/drain diffused layers 64 are shallow, the junction leak current can be suppressed.
Next, the method for fabricating the semiconductor device according to the present embodiment will be explained with reference to
First, the surface of the silicon substrate 34 is cleaned with, e.g., ammonia/hydrogen peroxide mixture. The silicon substrate 34 is, e.g., a p type silicon substrate with face orientation (100).
Next, on the silicon substrate 34, a silicon oxide film 36 of, e.g., a 50 nm-thickness is formed by, e.g., thermal oxidation (see
Next, a photoresist film 38 is formed by, e.g., spin coating. Then, the photoresist film 38 is patterned by photolithography. Thus, the photoresist mask 38 for patterning the silicon oxide film 36 is formed (see
Next, with the photoresist film 36 as the mask, the silicon oxide film 36 is etched (see
Next, with the photoresist film 38 and the silicon oxide film 36 as the mask, a dopant impurity is implanted into the silicon substrate 34 by, e.g., ion implantation. Thus, the well 40 of a prescribed conduction type is formed (see
After the well 40 has been formed, the photoresist film 38 is removed (see
Next, the device isolation region for defining a device region is formed by, e.g., STI (Shallow Trench Isolation) as follows.
First, a silicon nitride film 42 of, e.g., a 50 nm-thickness is formed on the silicon substrate 34 by, e.g., CVD (Chemical Vapor Deposition) (see
Next, the silicon nitride film 42 is patterned by photolithography and dry etching. Thus, the hard mask 42 for forming the trench for the silicon oxide film to be buried in is formed (see
Next, with the silicon nitride film 42 as the mask, the silicon substrate 34 is etched. Thus, trenches 44 are formed in the silicon substrate 34 (see
After the trenches 44 have been formed, the silicon nitride film 42 used as the mask is removed by, e.g., wet etching (see
Next, on the silicon substrate 34 with the trenches 44 formed in, a silicon oxide film of, e.g., a 30 nm-thickness is formed by, e.g., CVD.
Next, the silicon oxide film is polished by, e.g., CMP (Chemical Mechanical Polishing) until the surface of the silicon substrate 34 is exposed to remove the silicon oxide film on the silicon substrate 34.
Thus, the device isolation regions 46 of the silicon oxide film buried in the trenches 44 are formed (see FIG. 11B). The device isolation regions 46 define device regions.
Next, a photoresist film 48 is formed by, e.g., spin coating. Then, the photoresist film 48 is patterned by photolithography. Thus, the photoresist mask 48 for forming the channel doped layer is formed (see
Next, with the photoresist film 48 as the mask, a dopant impurity is implanted into the silicon substrate 34 by, e.g., ion implantation. Thus, the channel doped layer 50 is formed in the silicon substrate 34 (see
After the channel doped layer 50 has been formed, the photoresist film 48 used as the mask is removed.
Next, the dopant impurity in the channel doped layer 50 is activated by thermal processing of, e.g., 950° C. and 10 seconds.
Then, on the silicon substrate 34, the gate insulation film 52 of a silicon oxide film of, e.g., a 2 nm-thickness is formed by, e.g., thermal oxidation (see
Next, a polysilicon film 54 of, e.g., a 100 nm-thickness is formed on the entire surface by, e.g., CVD.
Next, a dopant impurity is implanted into the polysilicon film 54 by, e.g., ion implantation (see
Next, a photoresist film 56 is formed by, e.g., spin coating. Then, the photoresist film 56 is patterned by photolithography. Thus, the photoresist mask 56 for patterning the polysilicon film 54 is formed (see
Then, with the photoresist film 56 as the mask, the polysilicon film 54 is dry etched. Thus, the gate electrode 54 of polysilicon film is formed (see
After the gate electrode 54 has been formed, the photoresist film 56 used as the mask is removed.
Then, with the gate electrode 54 as the mask, a dopant impurity is implanted in the silicon substrate 34 on both sides of the gate electrode 54 by, e.g., ion implantation. To form the NMOS transistor, arsenic, for example, is used as the n type dopant impurity, and the conditions for the ion implantation are, e.g., a 1 keV acceleration voltage and a 1×1015 cm−2 dose. To form the PMOS transistor, boron, for example, is used as the p type dopant impurity, and the conditions for the ion implantation are, e.g., 0.5 keV acceleration voltage and a 1×1015 cm−2 dose. Thus, the shallow impurity diffused regions 58 forming the extension regions of the extension source/drain structure are formed (see
Next, a silicon oxide film 60 of, e.g., a 100 nm-thickness is formed on the entire surface by, e.g., CVD (see
Then, the silicon oxide film 60 is anisotropically etched by, e.g., RIE (Reactive Ion Etching). Thus, the sidewall insulation film 60 of silicon oxide film is formed on the side wall of the gate electrode 54 (see
Next, with the gate electrode 54 and the sidewall insulation film 60 as the mask, a dopant impurity is implanted in the silicon substrate 34 on both sides of the gate electrode 54 and the sidewall insulation film 60. To form the NMOS transistor, phosphorus, for example, is used as the n type dopant impurity, and the conditions for the ion implantation are an 8 keV acceleration voltage and a 1×1016 cm−2 dose. To form the PMOS transistor, boron, for example, is used as the p type dopant impurity, and the conditions for the ion implantation are, e.g., a 5 keV acceleration voltage and a 5×1015 cm−2 dose. Thus, the impurity diffused regions 62 forming the deep regions of the source/drain diffused layers are formed (see
Next, prescribed thermal processing is performed to activate the dopant impurities implanted in the impurity diffused regions 58, 62.
Thus, the source/drain diffused layers 64 formed of the extension region, i.e., the shallow impurity diffused region 58 and the deep impurity diffused region 62 are formed in the silicon substrate 34 on both sides of the gate electrode 54 (see
Next, a natural oxide film formed on the surface of the gate electrode 54 and the surfaces of the source/drain diffused layers 64 is removed by, e.g., hydrofluoric acid processing.
Next, an Ni film 66 of, e.g., a 20 nm-thickness is formed on the entire surface by, e.g., sputtering using an Ni target (see
Then, a protection film 68 of a titanium nitride (TiN) film of, e.g., a 5-50 nm-thickness is formed on the Ni film 66 by, e.g., PVD (Physical Vapor Deposition) (see
The protection film 68 can prevent the oxidation of the nickel film 66 and a nickel silicide film to be formed later.
When the substrate with the Ni film 66 formed on is mounted on a cassette for transporting the substrate with the Ni film 66 exposed or is loaded in the furnace of the RTA apparatus or the chamber of the film forming apparatus, they are contaminated with the Ni, and the Ni particles often adhere to other substrates, etc. mounted on the cassette or loaded in the furnace of the RTA apparatus and the chamber of the film forming apparatus. The protection film 68 is formed on the Ni film 66, whereby such secondary contamination with the Ni can be prevented.
Then, as the first thermal processing for the silicidation, thermal processing of, e.g., 270° C. and 30 seconds is performed by, e.g., RTA. This thermal processing reacts the Ni in the lower part of the Ni film 66 with the Si in the upper part of the gate electrode 54 with each other and the Ni in the lower part of the Ni film 66 and the Si in the upper parts of the source/drain diffused layers 64 with each other. Thus, Ni2Si films 70a, 70b are formed on the gate electrode 54 and on the source/drain diffused layers 64 (see
Then, the protection film 68 and the part of the Ni film 66, which have not reacted with the Si, are selectively removed, respectively (see
Next, as the second thermal processing for the silicidation, thermal processing of, e.g., 500° C. and 30 seconds is performed by, e.g., RTA. This thermal processing reacts the Ni2Si in the Ni2Si film 70a and the Si in the upper part of the gate electrode 54 with each other and the Ni2Si in the Ni2Si films 70b and the Si in the upper parts of the source/drain diffused layers 64 with each other. Thus, the NiSi films 72a, 72b are formed on the gate electrode 54 and on the source/drain diffused layers 64 (see
Thus, the NiSi film 72a, 72b are formed on the gate electrode 54 and on the source/drain diffused layers 64 by salicide process. The film thickness of the Ni film 66 and the conditions for the first and the second thermal processing are suitably set, whereby the NiSi films 72a, 72b of a required film thickness can be obtained. For example, the NiSi films 72a, 72b can have a film thickness of, e.g., below 20 nm including 20 nm.
As described above, the method for fabricating the semiconductor device according to the present embodiment is characterized mainly in that, after the Ni film 66 is formed relatively thick, the Si in the upper parts of the gate electrode 54 and the source/drain diffused layers 64 and the Ni in the lower part of the Ni film 66 are reacted with each other by the first thermal processing to form the Ni2Si films 70a, 70b on the gate electrode 54 and the source/drain diffused layers 64, the part of the Ni film 66, which has not reacted with the Si, is selectively removed, and then the Si in the upper parts of the gate electrode 54 and the source/drain diffused layers and Ni2Si in the Ni2Si film 70a, 70b are reacted with each other by the second thermal processing to form the NiSi films 72a, 72b on the gate electrode 54 and the source/drain diffused layers 64.
By the first thermal processing, the Si in the upper parts of the gate electrode 54 and the upper part of the source/drain diffused layers 64 and the Ni in the lower part of the Ni film 66, which are formed relatively thick, are reacted with each other to form the Ni2Si films 70a, 70b while suppressing the formation of NiSi2 crystals in the first thermal processing. Then, after the part of the Ni film 66, which has not reacted with the Si, is selectively etched off, by the second thermal processing the Si in the upper part of the gate electrode 54 and the upper parts of the source/drain diffused layers 64 and the Ni2Si in the Ni2Si films 70a, 70b are reacted with each other to form the NiSi film 72a, 72b, whereby the NiSi films 72a, 72b are prevented from being formed too thick. The film thickness of the NiSi films 72a, 72b can be controlled by suitably setting the thermal processing temperature, the thermal processing period of time, etc. of the first and the second thermal processing.
Thus, on the gate electrode 54 and the source/drain diffused layer 64, the NiSi film 72a, 72b of good quality can be formed in a required film thickness while the formation of NiSi2 crystals of high resistance is being suppressed. This makes it possible to decrease the roughness in the interface between the NiSi film 72a and the gate electrode 54 and in the interfaces between the NiSi films 72b and the source/drain diffused layers 64 and suppress the scatter of the sheet resistances of the surface of the gate electrode 54 and the surfaces of the source/drain diffused layers 64. The junction leak current can be suppressed.
Then, a silicon nitride film 74 of, e.g., a 50 nm-thickness is formed on the entire surface by, e.g., plasma CVD. The film forming temperature of the silicon nitride film 74 is, e.g., 500° C. The steps following the salicide process are performed at a temperature of, e.g., below 500° C. including 500° C. so as to suppress the agglomeration of the NiSi films 72a, 72b.
Next, on the silicon nitride film 74, a silicon oxide film 76 of, e.g., a 600 nm-thickness is formed by, e.g., plasma CVD (see
Then, the silicon oxide film 76 is planarized by, e.g., CMP (see
Next, by photolithography and dry etching, the contact hole 78a and the contact holes 78b are formed in the silicon oxide film 76 and the silicon nitride film 74 respectively down to the NiSi film 72a and down to the NiSi films 72b (see
Then, the barrier metal 80 of titanium nitride film of, e.g., a 50 nm-thickness is formed by, e.g., sputtering on the silicon oxide film 76 with the contact holes 78a, 78b formed in.
Next, the tungsten film 82 of, e.g., a 400 nm-thickness is formed on the barrier metal 80 by, e.g., CVD (see
Next, the tungsten film 82 and the barrier metal 80 are polished by, e.g., CMP until the surface of the silicon oxide film 76 is exposed. Thus, the contact plugs 84a, 84b of the barrier metal 80 and the tungsten film 82 are formed respectively in the contact holes 78a, 78b (see
Next, the inter-layer insulation film 86 is formed on the entire surface (see
After the inter-layer insulation film 86 has been formed, an interconnection layer (not illustrated) is suitably formed.
Thus, the semiconductor device according to the present embodiment shown in
Next, the result of evaluating the method for fabricating the semiconductor device according to the present embodiment will be explained with reference to
(Result of the Evaluation (Part 1))
The MOS transistor fabricated by the method for fabricating the semiconductor device according to the present embodiment was sectionally observed with a transmission electron microscope to evaluate the roughness in the interface between the silicon substrate and the nickel silicide film. The sectional observation was made on the interface between the source/drain diffused layer of the MOS transistor and the nickel silicide film formed on the source/drain diffused layer.
In Controls 1 to 3 shown in
In contrast to this, in Example 1 shown in
As evident in the electron microscopic pictures shown in
Based on the sectional observation with the transmission electron microscope, it is confirmed that the method for fabricating the semiconductor device according to the present embodiment can form NiSi film of good quality while suppressing the formation of NiSi2 film and can decrease the roughness in the interface between the silicon substrate and the NiSi film.
(Evaluation Result (Part 2))
The junction leak current of the source/drain diffused layer was measured on the MOS transistor fabricated by the method for fabricating the semiconductor device according to the present embodiment. The junction leak current was measured on the p type source/drain diffused layer of the PMOS transistor, in which boron was ion implanted.
In the measurement, as illustrated in
In
In
In
In
As evident from the respective plots shown in
Based on the results of Controls 4 and 5, it is found that when the Ni film is formed relatively thin, the junction leak current cannot be sufficiently decreased whether the temperature of the first thermal processing is high or low.
(Evaluation Result (Part 3))
Furthermore, the sheet resistance of the gate electrode was measured on the MOS transistor fabricated by the method for fabricating the semiconductor device according to the present embodiment. As the MOS transistor, the PMOS transistor was formed. The dopant impurity ion implanted in the gate electrode was boron. The gate length was 40 nm. The sheet resistance was measured on a plurality of samples respectively of Example 2 and Controls 4 to 6 described above, and the cumulative probabilities were plotted.
As evident from the comparison with the plots shown in
Based on the above-described measured results of the junction leak current and the sheet resistance, it is found that the method for fabricating the semiconductor device according to the present embodiment can decrease the junction leak current of the source/drain diffused layer and the sheet resistance of the upper part of the gate electrode, where the silicide film is formed.
As described above, according to the present embodiment, the Ni film 66 is formed relatively thick in above a prescribed thickness including the prescribed thickness, the lower part of the Ni film 66 is reacted with Si by the first thermal processing to form the Ni2Si films 70a, 70b, and after the part of the Ni film 66, which has not reacted with Si, is removed, the Ni2Si films 70a, 70b are reacted with Si by the second thermal processing to form the NiSi films 72a, 72b, whereby the NiSi film 72a, 72b of good quality can be formed in a prescribed film thickness while suppressing the formation of the NiSi2 film of high resistance. Accordingly, the roughness in the interface between the gate electrode 54 and the NiSi film 72a and in the interfaces between the source/drain diffused layers 64 and the NiSi films 72b can be made small, and the scatter of the sheet resistances of the surface of the gate electrode 54 and the surface of the source/drain diffused layer 64 can be suppressed. The junction leak current can be suppressed.
(A Modification)
The method for fabricating the semiconductor device according to a modification of the present embodiment will be explained.
The method for fabricating the semiconductor device according to the present modification is characterized in that the steps from the step of forming the Ni film 66 to the step of performing the first thermal processing of the above-described method for fabricating the semiconductor device are made continuously without the exposure to the atmospheric air.
First, the steps up to the step of forming the source/drain diffused layers 64 are the same as those of the method for fabricating the semiconductor device illustrated in
Next, a natural oxide film formed on the surface of the gate electrode 54 and the surfaces of the source/drain diffused layers 64 is removed by, e.g., hydrofluoric acid processing.
Then, the Ni film 66 of, e.g., a 20 nm-thickness is formed on the entire surface. The film thickness of the Ni film 66 is above 17 nm including 17 nm. The part of the Ni film 66, which has not reacted with Si, must be completely removed after the silicidation, and the film thickness of the Ni film 66 is preferably below 200 nm including 200 nm.
To form the Ni film 66, a film forming apparatus which can form plural kinds of metal films and perform thermal processing in one and the same chamber without the exposure to the atmospheric air is used. The film forming methods for forming the metal films in such film forming apparatus are, e.g., sputtering, vapor deposition, etc. Thus, the formation of the Ni film 66 and the formation of the protection film 68 of TiN film or others formed on the Ni film, and the first thermal processing can be continuously without the exposure to the atmospheric air.
Then, the protection film 68 of, e.g., a 5-50 nm-thickness TiN film is formed on the Ni film 66 continuously in the chamber where the Ni film 66 has been formed. The protection 68 is not limited to titanium nitride film. The protection film 68 can be, e.g., Ti film of a 5-30 nm-thickness.
In the present modification, after the Ni film 66 has been formed, the protection film 68 is formed continuously in the chamber where the Ni film 66 has been formed without transporting the substrate and making processing in another apparatus, etc. with the Ni film 66 exposed. Accordingly, the secondary contamination with the Ni can be effectively prevented.
Then, as the first thermal processing for the silicidation, thermal processing is performed by, e.g., RTA of, e.g., 270° C. and 30 seconds continuously in the chamber where the Ni film 66 and the protection film 68 have been formed. Thus, the Ni in the lower part of the Ni film 66 and the Si in the upper part of the gate electrode 54 are reacted with each other, and the Ni in the lower part of the Ni film 66 and the Si in the upper parts of the source/drain diffused layers 64 are reacted with each other. Thus, the NiSi film 70a is formed on the gate electrode 54, and the NiSi films 70b are formed on the source/drain diffused layers 64.
The steps following the first thermal processing are the same as those of the method for fabricating the semiconductor device illustrated in
As described above, in the method for fabricating the semiconductor device according to the present modification, the steps from the step of forming the Ni film 66 to the step of performing the first thermal processing are continuously made in one and the same chamber of the apparatus without the exposure to the atmospheric air. Thus, the surface of the Ni film 66 is prevented from being oxidized, and silicide film of good quality can be formed. Another thermal processing apparatus for making the first thermal processing is not necessary, which can increase the throughput of the fabrication process.
The protection film 68 is formed continuously in the chamber where the Ni film 66 has been formed, whereby the secondary contamination with the Ni can be effectively prevented.
The semiconductor device and the method for fabricating the same according to a second embodiment of the present invention will be explained with reference to
The semiconductor device according to the present embodiment is substantially the same in the structure as that of the semiconductor device according to the first embodiment but is different from the semiconductor device according to the first embodiment in the fabricating method.
That is, the method for fabricating the semiconductor device according to the present embodiment is characterized in that in the method for fabricating the semiconductor device according to the first embodiment, the Ni film 66 is amorphized by ion implantation of Ni ions before the first thermal processing for the silicidation.
The steps up to the step of forming the source/drain diffused layers 64 are the same as those of the method for fabricating the semiconductor device according to the first embodiment illustrated in
Next, a natural oxide film formed on the surface of the gate electrode 54 and the surfaces of the source/drain diffused layers 64 is removed by, e.g., hydrofluoric acid processing.
Then, an Ni film 66 of, e.g., a 20 nm-thickness is formed on the entire surface by, e.g., sputtering using an Ni target (see
Then, before the first thermal processing for the silicidation is performed, Ni ions are implanted into the Ni film 66 (see
Then, on the amorphized Ni film 66, a protection film 68 of, e.g., a 5-50 nm-thickness TiN film by, e.g., PVD (see
The steps following the formation of the protection film 68 are the same as those of the method for fabricating the semiconductor device according to the first embodiment illustrated in
As described above, in the method for fabricating the semiconductor device according to the present embodiment, the Ni film 66 is amorphized by implanting Ni ions into the Ni film 66 before the first thermal processing for the silicidation. Accordingly, in the silicidation process by the first thermal processing, the Ni in the Ni film 66 reacts with Si while being diffused at higher diffusion velocity in comparison with the Ni in the Ni film 66 which is not amorphized. Thus, the Ni2Si films 70a, 70b can be effectively formed stably by the first thermal processing, whereby the NiSi film 72a, 72b of good quality can be formed while the formation of NiSi2 film is more effectively suppressed.
In the present embodiment, the Ni film 66 is amorphized by implanting Ni ions. However, the method for amorphizing the Ni film 66 is not essentially limited to ion implantation. The Ni film 66 may be amorphized by, e.g., depositing Ni under conditions which make the sputter rate as high as, e.g., above 1 nm/second including 1 nm/second or making the pressure of argon (Ar) for sputtering higher than, e.g., above 5 mTorr including 5 mTorr. In the case that the Ni film 66 is nano-grained by such methods, the same effect as produced by the amorphization of the Ni film 66 can be produced. Here, nano-graining means that the grain diameter of the grains forming the metal film is made the nanometer-order.
Patent Reference 1 discloses that in the salicide process using Co film, a silicon substrate is amorphized before Co film is formed on the silicon substrate for the purpose of suppressing the abnormal growth (formation of spikes) of CoSix which is a cause for the junction leak current. However, the technique disclosed in Patent Reference 1 is for amorphizing the silicon substrate and is irrelevant to the method for fabricating the semiconductor device according to the present embodiment, in which the Ni film is amorphized in the salicide process using Ni film.
The semiconductor device and the method for fabricating the same according to a third embodiment of the present invention will be explained with reference to FIGS. 24 to 29B.
First, the structure of the semiconductor device according to the present embodiment will be explained with reference to
Device isolation regions 46 for defining device regions are formed in a silicon substrate 34. The device region on the left side of the drawing is an NMOS transistor formed region 96, and the device region on the right side of the drawing is a PMOS transistor formed region 98. A p type well (not illustrated) is formed in the silicon substrate 34 of the NMOS transistor formed region 96. An n type well (not illustrated) is formed in the silicon substrate 34 in the PMOS transistor formed region 98.
On the silicon substrate 34 in the NMOS transistor formed region 96, a gate electrode 54n of polysilicon film is formed with a gate insulation film 52 of silicon oxide film formed therebetween. On the gate electrode 54n, a nickel silicide film 72a of NiSi alone is formed. That is, the nickel silicide film 72a is formed of only nickel silicide of NiSi phase alone. The film thickness of the nickel silicide film 72a is, e.g., below 20 nm including 20 nm.
A sidewall insulation film 60 is formed on the side wall of the gate electrode 54n with the nickel silicide film 72a formed on.
In the silicon substrate 34 on both sides of the gate electrode 54n, source/drain diffused layers 64n formed of a shallow impurity diffused region 58n forming the extension region of the extension source/drain structure and a deep impurity diffused region 62n are formed. On the source/drain diffused layers 64n, nickel silicide films 72b of NiSi alone are formed. That is, the nickel silicide film 72b is formed of only nickel silicide of NiSi phase alone. The film thickness of the nickel silicide film 72b is, e.g., below 20 nm including 20 nm.
Thus, the NMOS transistor including the gate electrode 54n and the source/drain diffused layers 64n is formed on the silicon substrate 34 in the NMOS transistor formed region 96.
On the silicon substrate 34 in the PMOS transistor formed region 98, a gate electrode 54p of the polysilicon film is formed with a gate insulation film 52 of silicon oxide film. The gate electrode 54p further includes an Si1-xGex film 100a whose composition ratio x is 0<x<1 on the polysilicon film. The composition of the Si1-xGex film 100a is, e.g., Si0.76Ge0.24. On the Si1-xGex film 100a of the gate electrode 54p, a nickel silicide film 102a of NiSi1-xGex alone whose composition ratio x is 0<x<1 is formed. That is, nickel silicide film 102a is formed of only nickel silicide of NiSi1-xGex phase alone whose composition ratio x is 0<x<1. The composition ratio between the Ni and the Si1-xGex of the NiSi1-xGex of the nickel silicide film 102a is 1:1. Specifically, the composition ratio of the nickel silicide film 102a is, e.g., NiSi0.76Ge0.24. The film thickness of the nickel silicide film 102a is, e.g., below 20 nm including 20 nm.
A sidewall insulation film 60 is formed on the side wall of the gate electrode 54p with the nickel silicide film 102a formed on.
In the silicon substrate 34 on both sides of the gate electrode 54p, source/drain diffused layers 64p formed of a shallow impurity diffused region 58p forming the extension region of the extension source/drain structure and a deep impurity diffused region 62p are formed.
Hollows 104 are formed in the source/drain diffused layers 64p on both sides of the gate electrode 54p and the sidewall insulation film 60. In the hollows 104, Si1-xGex films 100b whose composition ratio x is 0<x<1 are buried. The composition of the Si1-xGex film 100b is the same as that of the Si1-xGex film 100a and is, e.g., Si0.76Ge0.24. As described above, the PMOS transistor of the semiconductor device according to the present embodiment has the Si1-xGex films 100b buried in the source/drain regions. Because of the lattice constant of Si1-xGex larger than that of Si, a compressive strain is exerted to the part of the silicon substrate 34, which is to be the channel layer. Thus, high hole mobility can be realized.
On the Si1-xGex films 100b buried in the hollows 104 in the source/drain diffused layers 64p, nickel silicide films 102b of NiSi1-xGex alone whose composition ratio x is 0<x<1 are formed. That is, the nickel silicide film 102b is formed of only nickel silicide of NiSi1-xGex phase alone whose composition ratio x is 0<x<1. The composition ratio of the Ni and Si1-xGex of NiSi1-xGex of the nickel silicide film 102b is 1:1. Specifically, the composition of the nickel silicide film 102b is the same as the composition of the nickel silicide film 102a, e.g., NiSi0.76Ge0.24. The film thickness of the nickel silicide film 102b is, e.g., below 20 nm including 20 nm.
Thus, the PMOS transistor including the gate electrode 54p and the source/drain diffused layers 64p is formed on the silicon substrate 34 in the PMOS transistor formed region 98.
On the silicon substrate 34 with the NMOS transistor and the PMOS transistor formed on, a silicon nitride film 74 is formed. On the silicon nitride film 74, a silicon oxide film 76 is formed.
In the silicon oxide film 76 and the silicon nitride film 74, contact holes 78a are formed down to the nickel silicide film 72a, 102a on the gate electrodes 54n, 54p. In the silicon oxide film 76 and the silicon nitride film 74, contact holes 78b are formed down to the nickel silicide films 72b, 102b on the source/drain diffused layers 64n, 64p.
Contact plugs 84a, 84b of a barrier metal 80 and a tungsten film 82 are buried respectively in the contact holes 78a, 78b.
On the silicon oxide film 76 with the contact plugs 84a, 84b buried in, an inter-layer insulation film 86 is formed. In the inter-layer insulation film 86, interconnection layers 106 are buried, electrically connected to the contact plugs 84a, 84b. The interconnection layer 106 is formed of a barrier metal 108 of tantalum film and a copper film 110.
On the inter-layer insulation film 86 with the interconnection layers 106 buried in, an inter-layer insulation film 112 is formed. In the inter-layer insulation film 112, interconnection layers 114 are buried, electrically connected to the interconnection layers 106. The interconnection layer 114 is formed of a barrier metal 116 of tantalum film and a copper film 118.
On the inter-layer insulation film 112 with the interconnection layers 114 buried in, electrodes 120 are formed, electrically connected to the interconnection layers 114. The electrodes 120 are formed of aluminum film.
Thus, the semiconductor device according to the present embodiment is constituted.
The semiconductor device according to the present embodiment is characterized mainly in that in the PMOS transistor in which compressive strain is exerted by the Si1-xGex films 100b to the part of the silicon substrate 34, which is to be the channel layer, the nickel silicide films 102a, 102b formed respectively on the Si1-xGex film 100a of the gate electrode 64p and on the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p are formed of only nickel silicide of NiSi1-xGex phase alone whose composition ratio x is 0<x<1.
That is, in the semiconductor device according to the present embodiment, no Ni(Si1-xGex)2 crystals are formed in the nickel silicide films 102a, 102b. No Ni(Si1-xGex)2 crystals are formed either in the interface between the nickel silicide film 102a and the Si1-xGex film 100a of the gate electrode 54p. No Ni(Si1-xGex)2 crystals are formed either in the interfaces between the nickel silicide films 102b and the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p. Here, the Ni(Si1-xGex)2 crystals mean mixed crystals whose composition ratio between Ni and Si1-xGex is 1:2. Ni(Si1-xGex)2 crystals have higher resistance in comparison with NiSi1-xGex crystals whose composition ratio between Ni and Si1-xGex is 1:1 and is a cause for the scatter of the sheet resistance and the junction leak current increase, as are the NiSi2 crystals.
As described above, the nickel silicide film 102a is formed of only nickel silicide of NiSi1-xGex phase alone, whereby the roughness in the interface between the NiSi1-x Gex film 102a and the Si1-xGex film 100a of the gate electrode 54p can be made small, and the scatter of the sheet resistance of the surface of the Si1-xGex film 100a of the gate electrode 54p can be suppressed. The nickel silicide films 102b are formed of only nickel silicide of NiSi1-xGex phase alone, whereby the roughness in the interfaces between the NiSi1-xGex films 102b and the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p can be made small, and the scatter of the sheet resistance of the surfaces of the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p can be suppressed.
The film thickness of the nickel silicide film 102b is as thin as, e.g., below 20 nm including 20 nm, and besides, the Ni(Si1-xGex)2 crystals, which are a cause for generating the junction leakage, are not formed down to the vicinity of the junctions of the source/drain diffused layers 64p, whereby the junction leak current can be suppressed even when the junction depths of the source/drain diffused layers 64p are shallow.
According to the present embodiment, the Si1-xGex films 100b buried in the source/drain regions of the PMOS transistor exert compressive strain to the channel layer of the PMOS transistor, whereby the operation speed of the PMOS transistor can be increased.
Next, the method for fabricating the semiconductor device according to the present embodiment will be explained with reference to
In the same way as in the method for fabricating the semiconductor device according to the first embodiment illustrated in
Next, on the entire surface, a silicon oxide film 122 of, e.g., a 40 nm-thickness is formed by, e.g., CVD.
Next, the silicon oxide film 122 is patterned by photolithography and dry etching. Thus, the silicon oxide film 122 on the PMOS transistor-to-be-formed region 98 and the device isolation region 46 defining the PMOS transistor-to-be-formed region 98 is removed and the silicon oxide film 122 is left selectively on the NMOS transistor-to-be-formed region 96 and the device isolation region 46 defining the NMOS transistor-to-be-formed region 96 (see
Then, with the silicon oxide film 122 as the mask, the silicon substrate 34 is etched by, e.g., RIE with a high selectivity ratio to the silicon oxide film. Thus, the hollows 104 of a 50 nm-depth are formed in the source/drain diffused layers 64p on both sides of the gate electrode 54p and the sidewall insulation film 60. At this time, the upper part of the gate electrode 54p of polysilicon film is etched off (see
Next, the Si surface is cleaned for 5 seconds with diluted hydrofluoric acid (e.g., HF:H2O=5:100), and with the silicon oxide film 122 as the mask, the Si1-xGex films 100a, 100b of, e.g., a 60 nm-thickness are epitaxially grown by, e.g., CVD selectively on the gate electrode 54p and in the hollows 104 (see
Thus, in the PMOS transistor-to-be-formed region 98, the Si1-xGex films 100b are buried in the hollows 104 of the source/drain diffused layers 64p. The gate electrode 54p includes the Si1-xGex film 100a on the polysilicon film.
Then, the silicon oxide film 122 formed in the NMOS transistor-to-be-formed region 96 is etched off (see
Then, a natural oxide film formed on the surface of the gate electrode 54n, the surfaces of the source/drain diffused layers 64n, the surface of the Si1-xGex film 100a of the gate electrode 54p and the surfaces of the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p is removed by, e.g., hydrofluoric acid processing.
Next, an Ni film 66 of, e.g., a 20 nm-thickness is formed on the entire surface by, e.g., sputtering using an Ni target (see
Next, on the Ni film 66, the protection film 68 of, e.g., a 10 nm-thickness TiN film is formed by, e.g., sputtering (see
Next, as the first thermal processing for the silicidation, thermal processing of, e.g., 270° C. and 30 seconds is performed by, e.g., RTA.
By the first thermal processing, in the NMOS transistor, in the same way as in the method for fabricating the semiconductor device according to the first embodiment, the Ni in the lower part of the Ni film 66 and the Si in the upper part of the gate electrode 54n are reacted with each other, and the Ni in the lower part of the Ni film 66 and the Si in the upper parts of the source/drain diffused layers 64n are reacted with each other. Thus, the Ni2Si film 70a is formed on the gate electrode 54n, and the Ni2Si films 70b are formed on the source/drain diffused layers 64n (see
By the first thermal processing, in the PMOS transistor, the Ni in the lower part of the Ni film 66 and the Si1-xGex in the upper part of the Si1-xGex film 100a are reacted with each other, and the Ni in the lower part of the Ni film 66 and the Si1-xGex in the upper parts of the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p are reacted with other. Thus, the Ni2Si1-xGex film 101a is formed on the Si1-xGex film 100a, and the Ni2Si1-xGex films 101b are formed on the Si1-xGex films 100b (see
Next, the protection film 68 and the part of the Ni film 66, which have not reacted with Si or Si1-xGex, are respectively selectively removed by wet etching (see
Next, as the second thermal processing for the silicidation, thermal processing of, e.g., 400° C. and 30 seconds is performed by, e.g., RTA. The second thermal processing may be performed at 300-500° C. for 10-120 seconds.
By the second thermal processing, in the NMOS transistor, in the same way as in the method for fabricating the semiconductor device according to the first embodiment, the Ni2Si in the Ni2Si film 70a and the Si in the upper part of the gate electrode 54n are reacted with each other, and the Ni2Si in the Ni2Si films 70b and the Si in the upper parts of the source/drain diffused layers 64n are reacted with each other. Thus, the NiSi film 72a is formed on the gate electrode 54n, and the NiSi films 72b are formed on the source/drain diffused layers 64n (see
By the second thermal processing, in the PMOS transistor, the Ni2Si1-xGex in the Ni2Si1-xGex film 101a and the Si1-xGex in the upper part of the Si1-xGex film 100a are reacted with each other, and the Ni2Si1-xGex in the Ni2Si1-xGex films 101b and the Si1-xGex in the upper parts of the Si1-xGex films 100b are reacted with each other. Thus, the NiSi1-xGex film 102a is formed on the Si1-xGex film 100a, and the NiSi1-xGex films 102b are formed on the Si1-xGex films 100b (see
Thus, by the salicide process, in the NMOS transistor, in the same way as in the method for fabricating the semiconductor device according to the first embodiment, the NiSi film 72a is formed on the gate electrode 54n, and the NiSi films 72b are formed on the source/drain diffused layers 64n. The film thickness of the Ni film 66 and the conditions for the first and the second thermal processing are suitably set to thereby form the NiSi films 72a, 72b in a required film thickness. For example, the NiSi films 72a, 72b can be formed in a thickness of below 20 nm including 20 nm.
By the salicide process, in the PMOS transistor, the NiSi1-xGex film 102a is formed on the Si1-xGex film 100a of the gate electrode 54p, and the NiSi1-xGex films 102b are formed on the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p. The film thickness of the Ni film 66 and the conditions for the first and the second thermal processing are suitably set to thereby form the NiSi1-xGex films 102a, 102b in a required film thickness. For example, the NiSi1-xGex films 102a, 102b can be formed in a thickness of below 20 nm including 20 nm.
As described above, the method for fabricating the semiconductor device according to the present embodiment is characterized mainly in that after the Ni film 66 has been formed relatively thick, first, the first thermal processing is performed to react, in the PMOS transistor, the Si1-xGex in the upper parts of the Si1-xGex film 100a of the gate electrode 54p and the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p and the Ni in the lower part of the Ni film 66 with each other to thereby form the Ni2Si1-xGex films 101a, 101b respectively on the Si1-xGex films 100a, 100b, and after the part of the Ni film 66, which has not reacted with the Si1-xGex, is selectively removed, the second thermal processing is performed to thereby react the Si1-xGex in the upper parts of the Si1-xGex films 100a, 100b and the Ni2Si1-xGex in the Ni2Si1-xGex films 101a, 101b with each other to form the NiSi1-xGex films 102a, 102b respectively on the Si1-xGex films 100a, 100b.
In the PMOS transistor, by the first thermal processing, the Si1-xGex in the upper parts of the Si1-xGex film 100a of the gate electrode 54p and the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p and the Ni in the lower part of the Ni film 66 formed relatively thick are reacted with each other, whereby by the first thermal processing, the Ni2Si1-xGex films 101a, 101b can be formed while the formation of the Ni(Si1-xGex)2 crystals is being suppressed. Then, after the part of the Ni film 66, which has not reacted with the Si1-xGex, is selectively etched off, by the second thermal processing, the Si1-xGex in the upper parts of the Si1-xGex films 100a, 100b and the Ni2Si1-xGex in the Ni2Si1-xGex films 101a, 101b are reacted with each other to form the NiSi1-xGex films 102a, 102b, whereby the NiSi1-xGex films 102a, 102b are prevented from being formed too thick. The film thickness of the NiSi1-xGex films 102a, 102b can be controlled by suitably setting the conditions for the first and the second thermal processing, such as thermal processing temperature, thermal processing period time, etc.
Thus, the NiSi1-xGex films 102a, 102b of good quality can be formed in a required film thickness on the Si1-xGex film 100a of the gate electrode 54p and the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p while the formation of Ni(Si1-xGex)2 crystals of high resistance is being suppressed. Thus, the roughness in the interface between the NiSi1-xGex film 102a and the Si1-xGex film 100a of the gate electrode 54p can be made small, and the scatter of the sheet resistance of the surface of the Si1-xGex film 100a of the gate electrode 54p can be suppressed. Also the roughness in the interfaces between the NiSi1-xGex films 102b and the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p can be made small, and the scatter of the sheet resistances of the surfaces of the Si1-xGex films 100b buried in the hollows 104 of the source/drain diffused layers 64p can be suppressed. The junction leak current can be suppressed.
Then, after the contact plugs 85a, 84b, etc. have been formed in the same way as in the method for fabricating the semiconductor device according to the first embodiment illustrated in
Thus, the semiconductor device according to the present embodiment illustrated in
In the method for fabricating the semiconductor device described above, the steps from the step of forming the Ni film 66 to the step of performing the first thermal processing may be performed continuously without the exposure to the atmospheric air, as in the method for fabricating the semiconductor device according to the modification of the first embodiment.
In the method for fabricating the semiconductor device described above, before the first thermal processing for the silicidation, the Ni film 66 may be amorphized by implanting Ni ions as in the method for fabricating the semiconductor device according to the second embodiment.
The semiconductor device and the method for fabricating the same according to a fourth embodiment of the present invention will be explained with reference to FIGS. 30 to 35B.
First, the structure of the semiconductor device according to the present embodiment will be explained with reference to
Device insulation regions 46 for defining an NMOS transistor formed region 96 and a PMOS transistor formed region 98 are formed in a silicon substrate 34 as in the semiconductor device according to the third embodiment.
On the silicon substrate 34 in the NMOS transistor formed region 96, a gate electrode 54n of polysilicon film is formed with a gate insulation film 52 of silicon oxide film formed therebetween. The gate electrode 54n further includes an Si1-x-yGexCy film 124a whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0 on the polysilicon film. The lattice constant of the Si1-x-yGexCy of the Si1-x-yGexCy film 124a is set smaller than the lattice constant of Si. The composition of the Si1-x-yGexCy film 124a is, e.g., Si0.98Ge0.011C0.009. On the Si1-x-yGexCy film 124a of the gate electrode 54n, a nickel silicide film 126a formed of NiSi1-x-yGexCy alone whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0 is formed. That is, the nickel silicide film 126a is formed of only nickel silicide of Si1-x-yGexCy phase alone whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0. The composition ratio between the Ni and the Si1-x-yGexCy of the NiSi1-x-yGexCy of the nickel silicide film 126a is 1:1. Specifically, the composition of the nickel silicide film 126a is NiSi0.98Ge0.011C0.009. The film thickness of the nickel silicide film 126a is, e.g., below 20 nm including 20 nm.
A sidewall insulation film 60 is formed on the side wall of the gate electrode 54n with the nickel silicide film 126a formed on.
In the silicon substrate 34 on both sides of the gate electrode 54n, source/drain diffused layers 64n formed of a shallow impurity diffused region 58n forming the extension region of the extension source/drain structure and a deep impurity diffused region 62n are formed.
Hollows 128 are formed in the source/drain diffused layers 64n on both sides of the gate electrode 54n and the sidewall insulation film 60. In the hollows 128, Si1-x-yGexCy films 124b whose composition ratios x, y satisfy 0<x<1, 0<y<0.01, 1−x−y>0 are buried. The lattice constant of the Si1-x-yGexCy of the Si1-x-yGexCy film 124b is set smaller than the lattice constant of Si. The composition of the Si1-x-yGexCy film 124b is the same as that of the Si1-x-yGexCy film 124a, e.g., Si0.98Ge0.011C0.009. As described above, the NMOS transistor of the semiconductor device according to the present embodiment has the Si1-x-yGexCy films 124b buried in the source/drain regions. Because of the lattice constant of the Si1-x-yGexCy of the Si1-x-yGexCy film 124b set smaller than the lattice constant of Si, tensile strain is exerted to the part of the silicon substrate 34, which is to be the channel layer. Thus, high electron mobility can be realized.
On the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n, nickel silicide films 126b of NiSi1-x-yGexCy alone whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0 are formed. That is, the nickel silicide film 126b is formed of only nickel silicide of NiSi1-x-yGexCy phase alone whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0. The composition ratio between the Ni and the Si1-x-yGexCy of the NiSi1-x-yGexCy of the nickel silicide film 126b is 1:1. Specifically, the composition of the nickel silicide film 126b is the same as the composition of the nickel silicide film 126a, e.g., NiSi0.98Ge0.011C0.009. The film thickness of the nickel silicide film 126b is, e.g., below 20 nm including 20 nm.
Thus, the NMOS transistor including the gate electrode 54n and the source/drain diffused layer 64n is formed on the silicon substrate 34 in the NOMS transistor formed region 96.
On the silicon substrate 34 in the PMOS transistor formed region 98, a gate electrode 54p of polysilicon film is formed with a gate insulation film 52 of silicon oxide film formed therebetween. On the gate electrode 54p, a nickel silicide film 72a of NiSi alone is formed. That is, the nickel silicide film 72a is formed of only nickel silicide of NiSi phase alone. The film thickness of the nickel silicide film 72a is, e.g., below 20 nm including 20 nm.
A sidewall insulation film 60 is formed on the side wall of the gate electrode 54p with the nickel silicide film 72a formed on.
In the silicon substrate 34 on both sides of the gate electrode 54p, source/drain diffused layers 64p formed of a shallow impurity diffused region 58p forming the extension region of the extension source/drain structure and a deep impurity diffused region 62p are formed. On the source/drain diffused layers 64p, nickel silicide films 72b of NiSi alone are formed. That is, the nickel silicide film 72b is formed of only nickel silicide of NiSi phase alone. The film thickness of the nickel silicide film 72b is, e.g., below 20 nm including 20 nm.
Thus, the PMOS transistor including the gate electrode 54p and the source/drain diffused layers 64p is formed on the silicon substrate 34 in the PMOS transistor formed region 98.
On the silicon substrate 34 with the NMOS transistor and the PMOS transistor formed on, a silicon nitride film 74 is formed. On the silicon nitride film 74, a silicon oxide film 76 is formed.
In the silicon oxide film 76 and the silicon nitride film 74, contact holes 78a are formed down to the nickel silicide film 126a, 72a on the gate electrodes 54n, 54p. In the silicon oxide film 76 and the silicon nitride film 74, contact holes 78b are formed down to the nickel silicide films 126b, 78b on the source/drain diffused layers 64n, 64p.
Contact plugs 84a, 84b of a barrier metal 80 and a tungsten film 82 are buried respectively in the contact holes 78a, 78b.
On the silicon oxide film 76 with the contact plugs 84a, 84b buried in, interconnection layers 106, 114, electrodes 120, etc. are formed, as in the semiconductor device according to the third embodiment.
Thus, the semiconductor device according to the present embodiment is constituted.
The semiconductor device according to the present embodiment is characterized mainly in that in the NMOS transistor in which tensile strain is exerted by the Si1-x-yGexCy films 124b to the part of the silicon substrate 34, which is to be the channel layer, the nickel silicide films 126a, 126b formed respectively on the Si1-x-yGexCy film 124a of the gate electrode 54n and on the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n are formed of only nickel silicide of NiSi1-x-yGexCy phase alone whose composition ratios x, y satisfy 0<x<1, 0<y<0.01 and 1−x−y>0.
That is, in the semiconductor device according to the present embodiment, no Ni(Si1-x-yGexCy)2 crystals are formed in the nickel silicide film 126a, 126b. No Ni(Si1-x-yGexCy)2 crystals are formed either in the interface between the nickel silicide film 126a and the Si1-x-yGexCy film 124a of the gate electrode 54n. No Ni(Si1-x-yGexCy)2 crystals are formed either in the interfaces between the nickel silicide films 126b and the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n. Here, the Ni(Si1-x-yGexCy)2 crystals mean the mix crystals whose composition ratio between Ni and Si1-x-yGexCy is 1:2. The Ni(Si1-x-yGexCy)2 crystals have higher resistance in comparison with the NiSi1-x-yGexCy crystals whose composition ratio between Ni and Si1-x-yGexCy is 1:1 and is a cause for the scatter of the sheet resistance and the junction leak current increase, as are the NiSi2 crystals.
As described above, the nickel silicide film 126a is formed of only nickel silicide of NiSi1-x-yGexCy phase alone, whereby the roughness in the interface between the Si1-x-yGexCy film 126a and the Si1-x-yGexCy film 124a of the gate electrode 54n can be made small, and the scatter of the sheet resistance of the surface of the Si1-x-yGexCy film 124a of the gate electrode 54n can be suppressed. The nickel silicide films 126b are formed of only nickel silicide of NiSi1-x-yGexCy phase alone, whereby the roughness in the interfaces between the NiSi1-x-yGexCy films 126b and the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n can be made small, and the scatter of the sheet resistance of the surfaces of the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n can be suppressed.
The film thickness of the nickel silicide film 126b is as thin as, e.g., below 20 nm including 20 nm, and besides, the Ni(Si1-x-yGexCy)2 crystals, which are a cause for generating the junction leak current, are not formed down to the vicinity of the junctions of the source/drain diffused layers 64n, whereby the junction leak current can be suppressed even when the junction depths of the source/drain diffused layers 64n are shallow.
According to the present embodiment, the Si1-x-yGexCy films 124b buried in the source/drain diffused regions of the NMOS transistor exert tensile strain to the channel layer of the NMOS transistor, whereby the operation speed of the NMOS transistor can be increased.
Next, the method for fabricating the semiconductor device according to the present embodiment will be explained with reference to
In the same way as in the method for fabricating the semiconductor device according to the first embodiment illustrated in
Next, on the entire surface, a silicon oxide film 130 of, e.g., a 40 nm-thickness is formed by, e.g., CVD.
Next, the silicon oxide film 130 is patterned by photolithography and dry etching. Thus, the silicon oxide film 130 on the NMOS transistor-to-be-formed region 96 and the device isolation region 46 defining the NMOS transistor-to-be-formed region 96 is removed and the silicon oxide film 130 is left selectively on the PMOS transistor-to-be-formed region 98 and the device isolation region 46 defining the PMOS transistor-to-be-formed region 98 (see
Then, with the silicon oxide film 122 as the mask, the silicon substrate 34 is etched by, e.g., RIE with a high selectivity ratio to the silicon oxide film. Thus, the hollows 128 of a 50 nm-depth are formed in the source/drain diffused layers 64n on both sides of the gate electrode 54n and the sidewall insulation film 60. At this time, the upper part of the gate electrode 54n of polysilicon film is etched off (see
Then, with the silicon oxide film 130 as the mask, an Si1-x-yGexCy film 124a, 124b of, e.g., a 60 nm-thickness is epitaxially grown by, e.g., CVD selectively on the gate electrode 54n and in the hollows 128 (see
Thus, in the NMOS transistor-to-be-formed region 96, the Si1-x-yGexCy films 124b are buried in the hollows 128 of the source/drain diffused layers 64n. The gate electrode 54n includes the Si1-x-yGexCy film 124a on the polysilicon film (
Then, the silicon oxide film 130 formed in the PMOS transistor-to-be-formed region 98 is etched off (see
Then, a natural oxide film formed on the surface of the Si1-x-yGexCy film 124a of the gate electrode 54n, the surfaces of the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n, the surface of the gate electrode 54p and the surfaces of the source/drain diffused layers 64p is removed by hydrofluoric acid processing.
Next, an Ni film 66 of, e.g., a 20 nm-thickness is formed on the entire surface by, e.g., sputtering using an Ni target (see
Next, on the Ni film 66, the protection film 68 of, e.g., a 10 nm-thickness TiN film is formed by, e.g., sputtering (see
Next, as the first thermal processing for the silicidation, thermal processing of, e.g., 270° C. and 30 seconds is performed by, e.g., RTA.
By the first thermal processing, in the NMOS transistor, the Ni in the lower part of the Ni film 66 and the Si1-x-yGexCy in the upper part of the Si1-x-yGexCy film 124a of the gate electrode 54n are reacted with each other, and the Ni in the lower part of the Ni film 66 and the Si1-x-yGexCy in the upper parts of the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n are reacted with each other. Thus, the Ni2Si1-x-yGexCy film 125a is formed on the Si1-x-yGexCy film 124a, and the Ni2Si1-x-yGexCy films 125b are formed on the Si1-x-yGexCy films 124b (see
By the first thermal processing, in the PMOS transistor, in the same way as in the method for fabricating the semiconductor device according to the first embodiment, the Ni in the lower part of the Ni film 66 and the Si in the upper part of the gate electrode 54p are reacted with each other, and the Ni in the lower part of the Ni film 66 and the Si in the upper parts of the source/drain diffused layers 64p are reacted with each other. Thus, the Ni2Si film 70a is formed on the gate electrode 54p, and the Ni2Si films 70b are formed on the source/drain diffused layers 64p (see
Next, the protection film 68 and the part of Ni film 66, which has not reacted with Si or Si1-x-yGexCy, are respectively selectively removed by wet etching (see
Next, as the second thermal processing for the silicidation, thermal processing of, e.g., 400° C. and 30 seconds is performed by, e.g., RTA. The second thermal processing may be performed at 300-500° C. and 10-120 seconds.
By the second thermal processing, in the NMOS transistor, the Ni2Si1-x-yGexCy in the Ni2Si1-x-yGexCy film 125a and the Si1-x-yGexCy in the upper part of the Si1-x-yGexCy film 124a are reacted with each other, and the Ni2Si1-x-yGexCy in the Ni2Si1-x-yGexCy films 125b and the Si1-x-yGexCy in the upper parts of the Si1-x-yGexCy films 124b are reacted with each other. Thus, the NiSi1-x-yGexCy film 126a is formed on the Si1-x-yGexCy film 124a, and the NiSi1-x-yGexCy films 126b are formed on the Si1-x-yGexCy films 124b (see
By the second thermal processing, in the PMOS transistor, in the same way as in the method for fabricating the semiconductor device according to the first embodiment, the Ni2Si in the Ni2Si film 70a and the Si in the upper part of the gate electrode 54p are reacted with each other, and the Ni2Si in the Ni2Si films 70b and the Si in the upper parts of the source/drain diffused layers 64p are reacted with each other. Thus, the NiSi film 72a is formed on the gate electrode 54p, and the NiSi films 72b are formed on the source/drain diffused layers 64p (see
Thus, by the salicide process, in the NMOS transistor, the NiSi1-x-yGexCy film 126a is formed on the Si1-x-yGexCy film 124a of the gate electrode 54n, and the NiSi1-x-yGexCy films 126b are formed on the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n. The film thickness of the Ni film 66 and the conditions for the first and the second thermal processing are suitably set to thereby form the NiSi1-x-yGexCy films 126a, 126b in a required film thickness. For example, the NiSi1-x-yGexCy films 126a, 126b can be formed in a thickness of below 20 nm including 20 nm.
By the salicide process, in the PMOS transistor, in the same way as in the method for fabricating the semiconductor device according to the first embodiment, the NiSi film 72a is formed on the gate electrode 54p, and the NiSi films 72b are formed on the source/drain diffused layers 64p. The film thickness of the Ni film 66 and the conditions for the first and the second thermal processing are suitably set to thereby form the NiSi film 72a, 72b in a required film thickness. For example, the NiSi films 72a, 72b can be formed in a thickness of below 20 nm including 20 nm.
As described above, the method for fabricating the semiconductor device according to the present embodiment is characterized in that after the Ni film 66 has been formed relatively thick, first, the first thermal processing is performed to react, in the NMOS transistor, the Si1-x-yGexCy in the upper parts of the Si1-x-yGexCy film 124a of the gate electrode 54n and the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n and the Ni in the lower part of the Ni film 66 with each other to thereby form the Ni2Si1-x-yGexCy films 125a, 125b respectively on the Si1-x-yGexCy films 124a, 124b, and after the part of the Ni film 66, which has not reacted with the Si1-x-yGexCy, is selectively removed, the second thermal processing is performed to thereby react the Si1-x-yGexCy in the upper parts of the Si1-x-yGexCy films 124a, 124b and the Ni2Si1-x-yGexCy in the Ni2Si1-x-yGexCy films 125a, 125b with each other to form the NiSi1-x-yGexCy films 126a, 126b respectively on the Si1-xGexCy films 124a, 124b.
In the NMOS transistor, by the first thermal processing, the Si1-x-yGexCy in the upper parts of the Si1-x-yGexCy film 124a of the gate electrode 54n and the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n and the Ni in the lower part of the Ni film 66 formed relatively thick are reacted with each other, whereby by the first thermal processing, the Ni2Si1-x-yGexCy films 125a, 125b can be formed while the formation of the Ni(Si1-x-yGexCy)2 crystals is being suppressed. Then, after the part of the Ni film 66, which has not reacted with the Si1-x-yGexCy, is selectively etched off, by the second thermal processing, the Si1-x-yGexCy in the upper parts of the Si1-x-yGexCy films 124a, 124b and the Ni2Si1-x-yGexCy in the Ni2Si1-x-yGexCy films 125a, 125b are reacted with each other to form NiSi1-x-yGexCy films 126a, 126b, whereby the NiSi1-x-yGexCy films 126a, 126b are prevented from being formed too thick. The film thickness of the NiSi1-x-yGexCy films 126a, 126b can be controlled by suitably setting the conditions for the first and the second thermal processing, such as thermal processing temperature, thermal processing period of time, etc.
Thus, the NiSi1-x-yGexCy films 126a, 126b of good quality can be formed in a required film thickness on the Si1-x-yGexCy film 124a of the gate electrode 54n and the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n while the formation of the Ni(Si1-x-yGexCy)2 crystals of high resistance is being suppressed. Thus, the roughness in the interface between the NiSi1-x-yGexCy film 126a and the Si1-x-yGexCy film 124a of the gate electrode 54n can be made small, and the scatter of the sheet resistance of the surface of the Si1-x-yGexCyfilm 124a of the gate electrode 54n can be suppressed. Also the roughness in the interfaces between the NiSi1-x-yGexCy films 126b and the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n can be made small, and the scatter of the sheet resistances of the surfaces of the Si1-x-yGexCy films 124b buried in the hollows 128 of the source/drain diffused layers 64n can be suppressed. The junction leak current can be suppressed.
Then, after the contact plugs 85a, 84b, etc. have been formed in the same way as in the method for fabricating the semiconductor device according to the first embodiment illustrated in
Thus, the semiconductor device according to the present embodiment illustrated in
In the method for fabricating the semiconductor device described above, the steps from the step of forming the Ni film 66 to the step of performing the first thermal processing may be performed continuously without the exposure to the atmospheric air, as in the method for fabricating the semiconductor device according to the modification of the first embodiment.
In the method for fabricating the semiconductor device described above, before the first thermal processing for the silicidation, the Ni film 66 may be amorphized by implanting Ni ions, as in the method for fabricating the semiconductor device according to the second embodiment.
The present invention is not limited to the above-described embodiments and can cover other various modifications.
For example, in the first and the second embodiments described above, the salicide process is made to form the NiSi films 72a, 72b on both of the gate electrode 54 and the source/drain diffused layers 64. However, the present invention is not limited to the case that the NiSi films 72a, 72b are formed on both the gate electrode 54 and the source/drain diffused layers 64 and is applicable to the case that the NiSi film is formed on either of the gate electrode 54 and the source/drain diffused layers 64.
In the third embodiment, the salicide process is made to form, in the PMOS transistor, the NiSi1-xGex film 102a, 102b on both the gate electrode 54p and the source/drain diffused layers 64p. However, the present invention is not limited to the case that the NiSi1-xGex films 102a, 102b are formed on both the gate electrode 54p and the source/drain diffused layers 64p and is applicable to the case that the NiSi1-xGex film is formed on either of the gate electrode 54p and the source/drain diffused layers 64p.
In the fourth embodiment, the salicide process is made to form, in the NMOS transistor, the Si1-x-yGexCy films 126a, 126b on both the gate electrode 54n and the source/drain diffused layers 64n. However, the present invention is not limited to the case that the NiSi1-x-yGexCy films 126a, 126b are formed on both the gate electrode 54n and the source/drain diffused layers 64n and is applicable to the case that the NiSi1-x-yGexCy film is formed on either of the gate electrode 54n and the source/drain diffused layer 64n.
In the third and the fourth embodiments described above, the compressive strain or the tensile strain is exerted to the part of the silicon substrate 34, which is to be the channel layer in either of the PMOS transistor and the NMOS transistor formed on one and the same silicon substrate 34. However, in the case that an NMOS transistor and a PMOS transistor are formed on one and the same silicon substrate 34, it is possible that the compressive strain is applied to the PMOS transistor, as in the third embodiment, and the tensile strain is applied to the NMOS transistor, as in the fourth embodiment.
In the above-described embodiments, the first and the second thermal processing is performed by RTA but is not essentially performed by RTA. For example, the first and the second thermal processing may be performed by furnace annealing, spike annealing or others. RTA thermal processing, furnace annealing and spike anneal may be combined.
The conditions for the first thermal processing are not limited to those of the above-described embodiments. In the first thermal processing, the thermal processing temperature can be, e.g., 200-400° C. The thermal processing period of time can be, e.g., 10 seconds-60 minutes.
The conditions for the second thermal processing are not limited to those of the above-described embodiments. The thermal processing temperature of the second thermal processing can be substantially the same as the thermal processing temperature of the first thermal processing or higher than the latter, specifically can be, e.g., 350-650° C. The thermal processing period of time can be, e.g., 20 seconds-60 minutes. Otherwise, as the second thermal processing, spike annealing of 450-650° C. may be performed.
In the above-described embodiments, the Ni film 66 is formed by sputtering. The Ni film 66 is not formed essentially by sputtering and can be formed by vapor deposition, e.g., electron beam vapor deposition, etc.
In the above-described embodiments, the protection film 68 is formed on the Ni film 66. However, the protection film 68 is not essential. When the substrate with the Ni film formed on is loaded with the Ni film exposed in a cassette for carrying substrates, the furnace of the RTA apparatus and the chamber of the film forming apparatus, particles of the Ni often adhere to other substrates, etc. loaded later in the cassette, the furnace of the RTA apparatus and chamber of the film forming apparatus. The protection film 68 formed on the Ni film 66 can prevent such secondary contamination with the Ni.
The semiconductor device and the method for fabricating the same according to the present invention can make it possible to suppress the scatter of the sheet resistance and the junction leak current of the source/drain diffused layer of a semiconductor device subjected to silicidation with nickel, and is useful to improve the operational characteristics and the yield of semiconductor devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-146763 | May 2004 | JP | national |
| 2004-294855 | Oct 2004 | JP | national |
This application is a Continuation of International Application No. PCT/JP2005/008536, with an international filing date of May 10, 2005, which designated the United States of America.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP05/08536 | May 2005 | US |
| Child | 11511472 | Aug 2006 | US |
