Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2000-11-20
2002-08-20
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S396000
Reexamination Certificate
active
06436757
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for fabricating a semiconductor device, and more specifically to a method for fabricating a capacitor having a capacitor dielectric film formed of Ta
2
O
5
(tantalum oxide) in a semiconductor device.
For microminiaturization of a semiconductor memory, it has become difficult to ensure a necessary capacitance only by increasing a surface area of a storage capacitor. Therefore, a method has been proposed which fabricates a semiconductor device having a capacitor having a capacitor dielectric film formed of Ta
2
O
5
(tantalum oxide) which has a relative dielectric constant remarkably larger than that of SiN (silicon nitride) being used in the prior art. However, the Ta
2
O
5
film has a problem that the Ta
2
O
5
film is inferior to the SiN film in heat resistant property and a leak current is large.
In order to overcome this problem, IEEE Electron Device Letter, P514, 1989 proposes a semiconductor device fabricating method in which a Ta
2
O
5
film is annealed in the presence of ultraviolet radiation and ozone (O
3
). Furthermore, Journal of Electrochemical Society, P1246, 1994 proposes a semiconductor device fabricating method in which a Ta
2
O
5
film is treated with an oxygen plasma.
However, these proposals have another problem as follows: In the semiconductor device fabricating method proposed by IEEE Electron Device Letter, P514, 1989, since ultraviolet is irradiated to the whole of the device, reliability of transistors is deteriorated. In the semiconductor device fabricating method proposed by Journal of Electrochemical Society, P1246, 1994, the Ta
2
O
5
film is damaged by the ion irradiation, and since the film quality cannot be improved over the whole surface of the capacitor dielectric film since ions and radials are not sufficiently uniformly irradiated in a coarse surface electrode structure.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a semiconductor device fabricating method which has overcome the above mentioned problems of the prior art.
Another object of the present invention is to provide a method for fabricating a capacitor having a capacitor dielectric film formed of Ta
2
O
5
(tantalum oxide) in a semiconductor device, the method being capable of improving the film quality over the whole surface of the capacitor dielectric film to realize a capacitor having an excellent heat resistance property and a good leak current characteristics and at the same time capable of maintaining a good reliability of a transistor.
The above and other objects of the present invention are achieved in accordance with the present invention by a method for fabricating a capacitor having a capacitor dielectric film formed of Ta
2
O
5
in a semiconductor device, the method comprising the step of:
forming a capacitor lower electrode on an insulating film formed on a semiconductor substrate;
forming a Ta
2
O
5
film on the capacitor lower electrode;
immersing the semiconductor substrate into a H
2
O
2
containing solution;
heat-treating the semiconductor substrate; and
forming a capacitor upper electrode on the Ta
2
O
5
film.
In the above mentioned capacitor fabricating method in accordance with the present invention, the oxygen vacancy density in the Ta
2
O
5
film is decreased by treating the Ta
2
O
5
film with the H
2
O
2
containing solution, with the result that the leak current of the capacitor having the capacitor dielectric film formed of Ta
2
O
5
is reduced.
Furthermore, the film quality of the Ta
2
O
5
film is improved by heat-treating the Ta
2
O
5
film, with the result that the leak current of the capacitor having the capacitor dielectric film formed of Ta
2
O
5
is reduced.
On the other hand, no ultraviolet radiation is carried out in the process for fabricating the capacitor and hence the semiconductor device having the capacitor. Therefore, it is possible to maintain a good reliability of the transistor, because the reliability of the transistor is in no way deteriorated by the ultraviolet radiation.
Since both the treatment with the H
2
O
2
containing solution and the heat treatment are an isotropic reaction, the Ta
2
O
5
film can be uniformly improved over the whole surface of the Ta
2
O
5
film even in a coarse surface electrode structure.
In one embodiment of the capacitor fabricating method in accordance with the present invention, the heat-treatment is conducted at a temperature not less than 700° C. Since crystallization of Ta
2
O
5
occurs at the temperature not less than 700° C., the film quality of the Ta
2
O
5
film is greatly improved. Accordingly, the effect of reducing the leak current of the capacitor can further be enhanced.
In a preferred embodiment of the capacitor fabricating method in accordance with the present invention, the heat-treatment is conducted in an oxidizing atmosphere. When the heat-treatment is conducted in the oxidizing atmosphere, oxygen is effectively absorbed in the Ta
2
O
5
film. Accordingly, the effect of reducing the leak current of the capacitor can further be enhanced.
In a specific embodiment of the capacitor fabricating method in accordance with the present invention, the heat-treatment is conducted in an oxygen containing atmosphere. Since the heat-treatment was conducted in the oxygen containing atmosphere, oxygen is effectively absorbed in the Ta
2
O
5
film. Accordingly, the effect of reducing the leak current of the capacitor can further be enhanced.
In a preferred embodiment of the capacitor fabricating method in accordance with the present invention, the H
2
O
2
containing solution has the H
2
O
2
concentration not less than 5%. If the H
2
O
2
concentration of the H
2
O
2
containing solution is not less than 5%, reactivity for compensating the oxygen vacancy in the Ta
2
O
5
film is intensified. Accordingly, the effect of reducing the leak current of the capacitor can further be enhanced.
In a more preferable embodiment of the capacitor fabricating method in accordance with the present invention, the temperature of the H
2
O
2
containing solution is no less than 60° C. If the temperature of the H
2
O
2
containing solution is no less than 60° C., reactivity for compensating the oxygen vacancy in the Ta
2
O
5
film is intensified. Accordingly, the effect of reducing the leak current of the capacitor can further be enhanced.
In addition, the time of immersing the semiconductor substrate into the H
2
O
2
containing solution is preferred to be not shorter than one minute, although the required immersing time depends upon the temperature of the H
2
O
2
containing solution and the H
2
O
2
concentration of the H
2
O
2
containing solution.
The above and other objects, features and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings.
REFERENCES:
patent: 6162738 (2000-12-01), Chen et al.
patent: 6214660 (2001-05-01), Uemoto et al.
McGinn & Gibb PLLC
NEC Corporation
Tsai Jey
LandOfFree
Method for fabricating a capacitor having a tantalum oxide... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for fabricating a capacitor having a tantalum oxide..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for fabricating a capacitor having a tantalum oxide... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2876809