Method of forming capacitor for semiconductor memory device

Details Method of forming capacitor for semiconductor memory device Method of forming capacitor for semiconductor memory device

2000-06-30

2002-01-08

Niebling, John F. (Department: 2812)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

Insulative material deposited upon semiconductive substrate

C438S253000, C438S254000, C438S255000, C438S256000, C438S396000, C438S397000, C438S398000, C438S399000

Reexamination Certificate

active

06337291

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming a capacitor for a semiconductor memory device. More particularly, the present invention relates to a method of forming a capacitor having a TaON film as a dielectric film, in a semiconductor memory device.
2. Description of the Prior Art
Along with the recent progress in the semiconductor manufacturing technology, the demand for memory device has increased dramatically. Generally, a memory device having high capacitance is desirable. Capacitance of the capacitor can be increased by using a dielectric layer having high dielectric constant or enlarging the surface area of a lower electrode. Those conventional capacitors are made with a Ta
2
O
5
layer having a dielectric constant higher than that of nitride-oxide(NO), thereby forming the lower electrode of 3-Dimensional structure.
However, as the Ta
2
O
5
film has an unstable stoichiometry, it must be subjected to an oxidation process for making it a stable state after being deposited. Upon this oxidation, the Ta
2
O
5
film is easily reacted with the lower electrode. This results in an increase in thickness of the effective dielectric film, thereby causing a decrease in capacitance of the capacitor. In addition, as the Ta
2
O
5
film is formed from an organic tantalum metal material as a precursor, there remain a large amount of carbon compounds in the Ta
2
O
5
film so that leakage current tends to generate.
To solve such drawbacks with the Ta
2
O
5
film, we have previously proposed a capacitor using a TaON film as a dielectric substance, as described in Korean Patent Application No. 99-24218. Such a capacitor using the TaON film as the dielectric substance is shown in FIG.
1
.
Referring to
FIG. 1
, a gate electrode
13
including a gate insulating layer
12
at a lower portion thereof is formed according to a known technique on the upper part of a semiconductor substrate
10
which a field oxide layer
11
is formed at a selected portion thereof. A junction region
14
is formed on the semiconductor substrate
10
at both sides of the gate electrode
13
, thereby forming an MOS transistor. A first interlevel insulating layer
16
and a second interlevel insulating layer
18
are formed on the upper part of the semiconductor substrate
10
in which the MOS transistor is formed. A storage node contact hole h is formed inside the first and the second interlevel insulating layers
16
,
18
so that a junction region
14
is exposed. A cylinder type lower electrode
20
is formed according to a known method, inside the storage node contact hole h so as to be in contact with the exposed junction region
14
. A HSG(hemi-spherical grain) layer
21
is formed on a surface of a lower electrode
20
to increase the surface area of the lower electrode
20
more. The surface of the lower electrode including the HSG layer
21
is thermal annealed at a temperature of 850° C. to 950° C. under a NH
3
plasma gas atmosphere for the purpose of preventing a natural oxide from being generated. A silicon nitride film
22
is formed by thermal annealing, on the lower electrode
20
including the HSG film
21
and on the second interlayer insulating film
18
. Natural oxidation reaction of the lower electrode
20
is restrained by forming the silicon nitride film
22
. On the silicon nitride film
22
, there is formed a TaON film
23
by a chemical vapor deposition of tantalum chemical vapor, NH
3
gas and O
2
gas. Then, the TaON film is crystallized by a thermal annealing, after which an upper electrode
25
is formed on the crystallized TaON film
23
. This TaON film
23
has a very high dielectric constant (∈=20 to 25), and consists of stable Ta—O—N bonds. For this reason, the TaON film
23
does not need to be subjected to an additional oxidization processing for the conversion into a stable state after being deposited, and also does not result in an increase in its thickness by virtue of its very low oxidation reactivity.
However, as the thermal annealing for the prevention of the natural oxidation film generation, which is carried out before the deposition of the TaON film
23
, is proceeded at 800° C. or above, the lower electrode
20
and other electrodes are melted that are made of material having a melting point of 800° C. or below. Thus, it is actually impossible to conduct the thermal processing at 800° C. or above.
Meanwhile, another method was previously proposed in which the thermal annealing before the deposition of the dielectric film is carried out at a temperature of 700° C. or below. However, if the thermal annealing is carried out at 700° C. or below, capacitance of the resulting capacitor can be increased as compared with the case of performing the thermal annealing at 800° C. or above as shown in
FIG. 2A
, whereas a leakage current characteristic can be deteriorated as shown in FIG.
2
B.
SUMMARY OF THE INVENTION
Accordingly, it is the object of the present invention to provide a method of manufacturing a capacitor for semiconductor memory devices capable of occurring less leakage current and obtaining high capacitance.
According to an embodiment of the present invention, there is provided a method of forming a capacitor on a semiconductor substrate, comprising the steps of: forming a lower electrode on the semiconductor substrate; forming an O
3
-oxide film on the lower electrode; forming Si—O—N bonds on the surface of the O
3
-oxide film; forming a TaON film on the Si—O—N bonds by a chemical vapor deposition of a Ta chemical vapor, an O
2
gas and a NH
3
gas; and forming an upper electrode on the TaON film.
According to another embodiment of the present invention, there is provided a method of forming a capacitor on a semiconductor substrate, comprising the steps of: forming a lower electrode on the semiconductor substrate; forming an O
3
-oxide film on the lower electrode by being supplied with an O
3
gas at a temperature of 200° C. to 500° C.; forming Si—O—N bonds on the surface of the O
3
-oxide film; forming a TaON film on the Si—O—N bonds by a chemical vapor deposition of a Ta chemical vapor, an O
2
gas and an NH
3
gas at a temperature of 300° C. to 600° C.; thermally processing the TaON film; and forming an upper electrode on the TaON film.


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