Capacitor in semiconductor device

Details Capacitor in semiconductor device Capacitor in semiconductor device

2002-10-11

2004-01-20

Lebentritt, Michael S. (Department: 2824)

Semiconductor device manufacturing: process

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

Having insulated gate

C438S240000, C438S393000, C438S396000

Reexamination Certificate

active

06680228

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a capacitor in a semiconductor device.
2. Description of the Related Art
Recently, the need for memory elements has increased with developments of techniques for manufacturing semiconductor devices. In a semiconductor device, a capacitor is used as a means for storing data. The capacitance of such a capacitor depends on the electrode area and the dielectric constant of a dielectric film interposed between electrodes of the capacitor.
However, as semiconductor devices become more highly integrated, the capacitor area given in the semiconductor device is reduced. Accordingly, the electrode area of the capacitor decreases, thereby causing a reduction in the capacitance of the capacitor.
In order to solve this problem, a capacitor comprising a TaON thin film of a high dielectric constant has been proposed, in which the TaON film has a metal film-insulating film-silicon (MIS) structure. An upper electrode over the TaON thin film is formed using a laminated structure composed of a polysilicon film deposited on a TiN film in order to enhance interface characteristics.
FIG. 1
is a cross-sectional view illustrating a conventional capacitor with a TaON thin film in a semiconductor device. As shown in
FIG. 1
, according to the conventional capacitor manufacturing method, a TaON thin film
2
having a high dielectric constant is deposited over a lower electrode
1
, for example, a polysilicon film.
Then, a TiN/polysilicon film
3
having a laminated structure is deposited over the TaON thin film
2
. The deposition of the TiN/polysilicon film
3
is achieved by forming a TiN thin film in a CVD (Chemical Vapor Deposition) chamber using TiCl
4
as a precursor and NH
3
as a reaction gas. Thus, a capacitor with an MIS structure is completely formed.
However, there are some problems involved in the conventional capacitor of a semiconductor memory device.
For example, as semiconductor devices become more highly integrated, the cell size is reduced, even though the capacitance per cell requisite for stably driving the device does not vary. Therefore, the TaON thin film having a single layer structure cannot assure a high enough capacitance of the capacitor and suppression of leakage current at the same time.
Also, after the deposition of the TaON thin film as a dielectric film and before the formation of the polysilicon film as an upper electrode, the formation of a TiN thin film has to be carried out in the CVD chamber using TiCl
4
as a precursor and NH
3
as a reaction gas in order to enhance the interface characteristics of the TaON thin film and the polysilicon film. Accordingly, there is an increase in the manufacturing costs for the additional process.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in order to solve the above-mentioned problems in the related art. An object of the present invention is to provide a capacitor in a semiconductor device, which is capable of achieving an improvement in the interface characteristics while assuring a high capacitance and a low leakage current.
In accordance with one aspect, the present invention provides a capacitor comprising: a lower electrode; a nitride film formed on the lower electrode; a TaON film formed over the nitride film; an Al
2
O
3
film formed over the TaON film; and an upper electrode formed on the Al
2
O
3
film film.


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