Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1998-07-23
2001-05-29
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S295000, C257S296000, C257S309000, C257S758000
Reexamination Certificate
active
06239462
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a semiconductor device and a method for fabricating the same. More particularly, the present invention relates to a semiconductor device including a capacitor device having a capacitive insulating film of insulating metal oxide film such as a ferroelectric film or a high dielectric film (i.e., a film made of a material having a high dielectric constant) and to a method for fabricating the same.
In recent years, as various electronic units such as microcomputers operating at an even higher speed and with even lower power consumption have been developed, the performance of consumer-use electronic units have also been further enhanced. Correspondingly, the sizes of semiconductor devices used for these units have also been rapidly reduced drastically.
As semiconductor devices have been miniaturized, unwanted radiation, i.e., electromagnetic wave noise generated from electronic units, has become a serious problem. Technology for incorporating a large-capacity capacitor device, including a ferroelectric film or a high dielectric film as a capacitive insulating film, into a semiconductor integrated circuit is now the object of much attention as a means for reducing the unwanted radiation.
On the other hand, since a very highly integrated dynamic RAM is now provided, researches have been widely carried out on technology for using a high dielectric film as a capacitive insulating film, instead of a silicon oxide film or a silicon nitride film, which has been conventionally used.
Furthermore, in order to put into practical use a non-volatile RAM operating with a low voltage and enabling high-speed write and read operations, researches and developments have also been vigorously carried out on a ferroelectric film having spontaneous polarization properties. A ferroelectric memory using a ferroelectric film as a capacitive insulating film takes advantage of a phenomenon that the amount of charge flowing into/out of a data line of a ferroelectric memory differs depending upon whether or not the spontaneous polarization of the ferroelectric film is inverted.
In all of these types of semiconductor devices mentioned above, it is an urgent task to develop technology for realizing very high integration for a capacitor device without deteriorating the characteristics thereof.
Hereinafter, a conventional semiconductor device will be described with reference to FIG.
13
.
FIG. 13
illustrates a cross-sectional structure of a conventional semiconductor device. As shown in
FIG. 13
, a lower electrode
2
made of a first platinum film, a capacitive insulating film
3
made of a ferroelectric film and an upper electrode
4
made of a second platinum film are formed in this order on a semiconductor substrate
1
made of silicon. The lower electrode
2
, the capacitive insulating film
3
and the upper electrode
4
constitute a capacitor device. An interlevel insulating film
5
made of a silicon oxide film, a silicon nitride film or the like is deposited to cover the entire surface of the semiconductor substrate
1
as well as the capacitor device. A lower-electrode contact hole
6
and an upper-electrode contact hole
7
are formed through the interlevel insulating film
5
. Metal interconnections
8
, each consisting of a titanium film
8
a
, a first titanium nitride film
8
b
, an aluminum film
8
c
and a second titanium nitride film
8
d
, are formed to cover the interlevel insulating film
5
as well as the inner surfaces of the lower-electrode contact hole
6
and the upper-electrode contact hole
7
.
Hereinafter, a method for fabricating the conventional semiconductor device will be described with reference to FIGS.
14
(
a
) through
14
(
e
).
First, as shown in FIG.
14
(
a
), the first platinum film
2
A, the ferroelectric film
3
A and the second platinum film
4
A are sequentially stacked over the entire surface of the semi-conductor substrate
1
. Thereafter, as shown in FIG.
14
(
b
), the second platinum film
4
A is selectively etched, thereby forming the upper electrode
4
. Then, in order to recover and stabilize the crystal structure of the ferroelectric film
3
A, the ferroelectric film
3
A is subjected to a heat treatment within oxygen ambient.
Next, as shown in FIG.
14
(
c
), the ferroelectric film
3
A and the first platinum film
2
A are selectively etched, thereby forming the capacitive insulating film
3
out of the ferroelectric film
3
A and the lower electrode
2
out of the first platinum film
2
A. Then, in order to recover and stabilize the crystal structure of the ferroelectric film constituting the capacitive insulating film
3
, the capacitive insulating film
3
is subjected to a heat treatment within oxygen ambient.
Subsequently, as shown in FIG.
14
(
d
), the interlevel insulating film
5
made of a silicon oxide film or a silicon nitride film is deposited over the entire surface of the semi-conductor substrate
1
. And the lower-electrode contact hole
6
and the upper-electrode contact hole
7
are formed through the interlevel insulating film
5
. Then, in order to recover and stabilize the crystal structure of the ferroelectric film constituting the capacitive insulating film
3
, the capacitive insulating film
3
is subjected to a heat treatment within oxygen ambient.
In order to prevent the lower electrode
2
or the upper electrode
4
from being oxidized as a result of the reaction between the lower electrode
2
or the upper electrode
4
with the capacitive insulating film
3
during the heat treatment conducted to recover and stabilize the crystal structure of the ferroelectric film, the lower and the upper electrodes
2
,
4
are made of platinum, which is hard to react with the ferroelectric film
3
A constituting the capacitive insulating film
3
during the heat treatment and exhibits anti-oxidation properties even at a high temperature.
Then, as shown in FIG.
14
(
e
), the titanium film
8
a
, the first titanium nitride film
8
b
, the aluminum film
8
c
and the second titanium nitride film
8
d
are sequentially deposited to cover the entire surface of the semiconductor substrate
1
as well as the inner surfaces of the lower-electrode contact hole
6
and the upper-electrode contact hole
7
, thereby forming the metal interconnections
8
, each consisting of the titanium film
8
a
, the first titanium nitride film
8
b
, the aluminum film
8
c
and the second titanium nitride film
8
d
. The titanium film
8
a
functions as an adhesive film for improving the adhesion between the aluminum film
8
c
and the platinum film constituting the upper electrode
4
. The first titanium nitride film
8
b
functions as a barrier film for preventing aluminum in the aluminum film
8
c
from diffusing into the capacitive insulating film
3
. The second titanium nitride film
8
d
functions as an anti-reflection film while an upper inter level insulating film deposited over the metal interconnections
8
is etched.
Next, in order to further improve the adhesion between the titanium film
8
a
constituting the metal interconnections
8
and the interlevel insulating film
5
, the metal interconnections
8
are subjected to a heat treatment.
However, during the heat treatment conducted to stabilize the crystal structure of the ferroelectric film, the platinum film constituting the upper electrode comes to have column like crystal structure. Thus, during the heat treatment conducted to improve the adhesion between the metal interconnections and the interlevel insulating film, the titanium atoms in the titanium film constituting the metal interconnections adversely pass through the grain boundary of the column like crystals of the platinum film constituting the upper electrode so as to diffuse into the capacitive insulating film. As a result, since the composition of the ferroelectric film or the high dielectric film constituting the capacitive insulating film is varied, the electrical characteristics of the capacitor device are disadvantageously deteriorated.
It is not only when the uppe
Ito Toyoji
Izutsu Yasufumi
Kutsunai Toshie
Matsuda Akihiro
Mikawa Takumi
Fenty Jesse A.
Jackson, Jr. Jerome
Matsushita Electronics Corporation
McDermott & Will & Emery
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