Patent Application
20070052042
The present invention generally relates to an improvement of a semiconductor device in which a high relative permittivity (high-k) film is used as a gate insulation film.
In the conventional technology, polysilicon (Poly-Si) is mainly used as an electrode material which is formed on a silicon substrate. As a gate insulation film provided between the silicon substrate and the polysilicon electrode material, a silicon oxide (SiO2), a silicon oxynitride (SiON), and a silicon nitride (Si3N4) are used. As a related matter, in order to increase the capacity (proportional to ε/d, where ε is relative permittivity, and d is film pressure.) of the gate insulation film, the thickness of the gate insulation film (SiO2 (ε=3.9)) is conventionally reduced.
According to Japanese Laid-Open Patent Application No. 2000-294550, a method is disclosed wherein a gate insulation film having a dioxide layer approximately equal in thickness to at most 1 nm is provided by performing an oxidation, nitriding, and oxynitriding directly on the surface of the wafer W by plasma processing.
There is a limitation to reducing the thickness of the gate insulation film; however, a method is presently suggested wherein the physical thickness of the layer can be increased to a certain extent by using a material having a high relative permittivity (High-K, where K is an equivalent to E).
A conventional High-K film is made from oxide; however, an oxide seed film is indispensable in forming an oxide film. Further, it is necessary to perform a high heating treatment in an atmosphere of the oxide seed or inert gas seed so as to stabilize the crystallinity of the oxide. As a result, SiO2 (or a metal mixture including Si, 0, and a High-K material) is formed on the Si surface or on the surface of the oxide High-K film. Accordingly, layers having a low relative permittivity are formed serially. Therefore, the original object of increasing the capacity cannot be achieved.
Accordingly, a method is suggested for providing a silicon nitride film (ε is about 7) between the Si surface and High-K material so as to prevent the SiO2 film from being formed. However, the silicon nitride film is oxidized while the High-K film is formed. Thus, it is difficult to form only a film having a high relative permittivity.
The present invention was made in consideration of the above described problems. It is a general object of the present invention to provide a semiconductor device having good quality by keeping the relative permittivity of a High-K insulation film in a high state. Another object of the present invention is to provide a method for manufacturing a semiconductor device in which the relative permittivity of the High-K insulation film can be kept in a high state.
In order to achieve the above described objects, a semiconductor device is provided including a silicon substrate, a gate electrode layer, and a gate insulation film between the silicon substrate and the gate electrode layer. The gate insulation film is a high relative permittivity (high-k) film being formed by performing a nitriding treatment on mixture of a metal and silicon. In other words, the High-K film itself is a nitride so as to prevent SiO2 from being formed.
As for the above described gate insulation film, it is preferable to form the film according to a plasma CVD technology. Further, in a case where a silicon nitride film is provided as a barrier layer between the silicon substrate and the gate insulation film, it is less likely that the thickness of the film increases while the High-K material is being formed. Thus, a decrease of the capacity can be controlled. This is based on the fact that the thickness of the silicon nitride film is less likely to increase than the thickness of the oxide film. It should be noted that the above described silicon nitride layer can be formed according to a direct nitriding by plasma processing.
Moreover, a silicon nitride film is provided on the gate insulation film so as to control a reaction with the gate electrode.
Furthermore, a more stable insulation film can be obtained by laminating the silicon nitride films and the gate insulation films alternately on the silicon substrate.
Further, interfacial quality can be improved and a good FET quality can be obtained by forming a buffer layer between the silicon substrate and the gate insulation film.
In addition, the relative permittivity of the buffer layer can be increased to substantially 9 by forming an Alumina (Al2O3) monocrystal film between the silicon substrate and the gate insulation film. Accordingly, the capacity can be further increased. It should be noted that the above described alumina monocrystal film can be formed according to the plasma CVD technology.
As for the above described gate insulation film, one of the following compositions can be adopted:
On the upper side of the treatment container 11, an open part corresponding to the silicon wafer W on the substrate holding board 12 is provided. The above open part is attached a dielectric board 13 which includes quartz, Al2O3, AlN, and Si3N4. On the upper side of the dielectric board 13, (outside of the treatment container 11) a plane antenna 14 is disposed. On the plane antenna 14, plural slots are provided so that an electromagnetic wave which is supplied from a wave guide 18 can permeate via the slots. On the further upper side (outside) of the plane antenna 14, a wavelength shortening board 15 and the wave guide 18 are provided. On the outside of the treatment container 11, a cooling plate 16 is disposed so as to cover the upper side of the wavelength shortening board 15. In the cooling plate 16, a coolant path 16a in which a coolant flows is provided.
On the side wall of the inside of the treatment container 11, a gas feed opening 22 is provided for introducing a gas when performing a plasma treatment. A separate gas feed opening 22 can be provided for each gas to be introduced. In this case, a mass flow controller of which the drawing is omitted is provided as means for flow control on each gas feed opening 22. As a related matter, a gas feed opening 22 can be a nozzle to which gases to be introduced being mixed in advance are supplied. In this case, the flow of the gas to be introduced is controlled by a flow regulating valve in the step of mixing the gas.
Moreover, in the inside of the wall of the treatment container 11, a coolant flow path 24 is provided so as to surround the treatment container 11.
The plasma treatment apparatus 10 used in the present invention embeds an electromagnetic wave generator generating a few GHz electromagnetic wave for exciting plasma, of which a drawing is omitted. The microwave generated by the electromagnetic wave generator propagates through the wave guide 18 and is introduced into the treatment container 11.
With reference to
As the High-K film 104, for example, one of the following compositions can be adopted:
When forming a configuration according to the first embodiment using the plasma treatment apparatus 10 shown in
The microwave having a few GHz generated by the electromagnetic wave generator is supplied to the treatment container 11 via the wave guide 18. The microwave is introduced into the treatment container 11 via the plane antenna 14 and the dielectric board 13. The microwave excites the plasma, and thus a nitride radical is generated. The temperature of the wafer is less than 500° C. when performing a plasma treatment thereon by using the plasma as above generated. The high density plasma which is generated by exciting the microwave in the treatment container 11 forms a nitride film Si3N4 on the surface of the silicon substrate 100.
The silicon substrate 100 on which the Si3N4 film 102 is formed is taken out of the treatment container 11. After the silicon substrate 100 is taken out, when forming a High-K film 104, the silicon substrate 100 is set in the treatment container 11 again, and the nitride film 104 is formed according to the well-known CVD technology.
The buffer layer 110 is formed by changing the composition of the gas which is supplied to the treatment container 11 in the same process of forming the High-K film 104. The buffer layer 110 has the benefit of a relative permittivity higher than that of the Si3N4 layer, and an interface state which can be lowered.
Further, the best mode for carrying out the invention and the embodiments are described based on some examples. The present invention is not limited to these embodiments, but variations and modifications may be made without departing from the scope of the present invention.
The present application is based on Japanese Priority Application No. 2003-100170 filed on Apr. 3, 2003, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-100170 | Apr 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/04700 | 3/31/2004 | WO | 9/27/2006 |
