Method of manufacturing a capacitor in a semiconductor...

Details Method of manufacturing a capacitor in a semiconductor... Method of manufacturing a capacitor in a semiconductor...

1999-12-20

2001-12-11

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S386000, C438S393000, C438S396000, C438S250000

Reexamination Certificate

active

06329237

ABSTRACT:

FIELD OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor technology. In particular, the present invention relates to a method of making a high dielectric capacitor in a semiconductor device, in which Ta
2
O
5
, BST((Ba
1−x
Sr
x
)TiO
3
) etc. having a high dielectric characteristic are used as capacitor dielectric films in a very high integrated memory device.
2. Description of the Prior Art
As the integration degree of a semiconductor device including DRAMs becomes higher, securing a sufficient static capacitance of a capacitor becomes problematic. As one of the solutions to solve this problem, a lot of efforts have been made to increase the surface area of the charge storage electrode, that is the underlying electrode of the capacitor. However, due to decrease of a process margin accompanied by the higher integration, there has been a limitation in increasing the surface area of the charge storage electrode.
In order to overcome this limitation, interest has been increased to technology for manufacturing a high dielectric capacitor using high dielectric materials such as tantalum oxide films, BST etc., which have a high dielectric characteristic, as capacitor dielectric films. The technology employs the principle in which the static capacitance of a capacitor is proportional to the dielectric rate.
The process of manufacturing the dielectric capacitor is normally similar to that of the NO (Nitride/Oxide) capacitor. However, it additionally includes technology of forming a thin film using tantalum oxide film, BST etc. having high dielectric materials, and process of pre • post processing technology etc. for preventing deterioration of an electric characteristic in the capacitor.
In case of using the BST thin film as the capacitor dielectric film, it uses Ba(C
11
H
19
O
2
)
2
, Sr(C
11
H
19
O
2
)
2
, and Ti(C
3
H
7
O)
2
. Therefore, it may include large amount of carbon within the thin film and also may cause the defects of oxygen depletion upon deposition of the thin film. Thus, it will increase a leak current to deteriorate the electric characteristic of the capacitor. Even though, any post processing technology to overcome these problems has not been made so far.
Also, in case of using the tantalum oxide film as the capacitor dielectric film, there have problems similar to those occurring when using BST thin films. It has usually performed an UV-O
3
process, a plasma process such as O
2
or N
2
O gases. etc., as subsequent processes for removing carbon from the tantalum oxide film or solving the oxygen depletion.
In case of UV-O
3
process, it must be performed under a semi-constant pressure or a constant pressure state in order to keep oxygen activated. Thus, at high pressure, as the average freedom pass of Oxidant is short, so the lifetime of Oxidant is short. Thus, in order to overcome this problem, the distance between the UV-lamp and the wafer must be extremely narrowed and also controlled with extra care, thus causing many limitations in process. Additionally, in case of using the plasma process such as O
2
or N
2
O gases, since O
2
gas become relatively less activated compared to N
2
O gas, it has a low effect of processing Ta
2
O
5
thin film compared to N
2
O gas. Also, if the plasma excites N2O gas, it will be decomposed to create oxygen ions or nitrogen ions, which then will eliminate the removal of carbon within the tantalum oxide film and the defects of oxygen depletion. However, nitrogen ions may damage Ta
2
O
5
thin films, thus it may cause the problem of deteriorating an electrical characteristic of the device.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problems involved in the prior art, and to provide a method of manufacturing a high dielectric capacitor of a semiconductor device, which can effectively remove carbon contained within the thin film after deposition of the BST film and defects of oxygen depletion caused upon deposition of the thin film.
Further, another object of the present invention is to provide a method of manufacturing a high dielectric capacitor of a semiconductor device, which can remove carbon contained within the thin film after deposition of the tantalum oxide film and defects of oxygen depletion caused upon deposition of the thin film, without further difficult processes or without any deterioration of the electrical characteristic of the capacitor.
The present invention employs the technology capable of effectively removing defects of carbon and oxygen depletion within the thin film, by forming a plasma O
3
gas having a good reactivity and by processing the plasma for the BST thin film and tantalum oxide film. It can extend the lifetime of the activated oxygen of oxygen, which had been a problem in processing a conventional UV-O
3
, by means of plasma process using O
3
gas. Thus, it can effectively remove defects of carbon and oxygen within the BST thin film and tantalum oxide film without complicating the process or deteriorating the electrical characteristic of the capacitor. The present invention also proposes a detailed process condition, which can optimize the plasma process using O
3
gas.
In order to accomplish the above object, a method of manufacturing a capacitor in a semiconductor device using a high dielectric tantalum oxide that is treated in an ozone plasma according to the present invention comprises a first step of forming a conductive film for an underlying electrode on a given underlying layer; a second step of forming a tantalum oxide film on the conductive film for the underlying electrode; a third step of performing a plasma process using ozone gas to remove defects and to crystallize the tantalum oxide film; and a fourth step of forming a conductive film for an upper electrode on the tantalum oxide film.


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F.-X. Jiang and S. K. Kurinec, “Tantalum Oxide Thin Films for Microelectronic Applications,” IEEE Proceedings of the Eleventh Biennial University/Government/Industry Microelectronics Symposium, May 1995, pp. 101-104.

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