Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2003-03-20
2004-11-16
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S240000, C438S250000, C438S003000, C438S957000, C257S535000, C257S532000
Reexamination Certificate
active
06818498
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a capacitance element using a capacitance insulating film made of a dielectric material with a high dielectric constant or of a ferroelectric material and to a manufacturing method therefor.
As higher-speed and lower-power microcomputers,have been implemented in recent years, electronic devices to be used as consumer products have remarkably increased in performance, while semiconductor elements composing a semiconductor device used therein have been rapidly scaled down. Under such circumstances, undesired radiation which is electromagnetic noise generated from the electronic devices has presented a serious problem. As a measure to suppress the undesired radiation, attention has been focused on the technique of embedding, in a semiconductor integrated circuit or the like, a capacitance element with large capacitance using a capacitance insulating film made of a dielectric material with a high dielectric constant (hereinafter simply referred to as a high-dielectric-constant material). As higher integration has been achieved in a dynamic RAM, on the other hand, extensive research has been conducted on the technique of using a high-dielectric-constant film as a replacement for a silicon oxide film or silicon nitride film that has been used previously. Additionally, vigorous research and development has been directed toward a ferroelectric film having the property of spontaneous polarization to implement an industrially usable non-volatile RAM capable of operating at low voltage and performing high-speed writing and reading operations.
To implement a semiconductor device having the performance described above, it is important to devise a capacitance element having such a structure as to allow higher integration without degrading the properties of the capacitance element and a manufacturing method therefor.
Referring to the drawings, a conventional capacitance element and a manufacturing method therefor will be described.
FIG. 9
is a cross-sectional view of a principal portion of the conventional capacitance element, in which are shown: a substrate
21
such as a silicon substrate with an integrated circuit formed therein; a lower electrode
22
of the capacitance element which is composed of a platinum film or the like; a capacitance insulating film
23
of the capacitance element which is composed of a thin ferroelectric film; and an upper electrode
24
of the capacitance element which is composed of a platinum film or the like. The upper and lower electrode
24
and
22
and the capacitance insulating film
23
constitute the capacitance element. There are also shown: an aperture
25
formed in the capacitance insulating film
24
; an interlayer insulating film
26
covering the capacitance element; a first contact hole
27
extending through the interlayer insulating film
26
to reach the lower electrode
22
; a second contact hole
28
extending through the interlayer insulating film
26
to reach the upper electrode
24
; a first electrode wire
29
to be connected to the lower electrode
22
; and a second electrode wire
30
to be connected to the upper electrode
24
.
The recent trend has been to compose each of the electrode wires
29
and
30
of a multilayer film such as a two-layer film consisting of an upper-layer aluminum-alloy film containing aluminum as a main component and a lower-layer titanium film or a three-layer film consisting of an upper-layer aluminum-alloy film containing aluminum as a main component, an interlayer titanium nitride film, and a lower-layer titanium film. In the case of embedding such a capacitance element in an integrated circuit, in particular, the first and second electrode wires
29
and
30
are also connected directly to a diffusion region in the integrated circuit, so that the titanium film is normally used to compose the lowermost layer of the multilayer film, thereby lowering contact resistance between the diffusion region and the aluminum alloy film.
Next, a description will be given to the manufacturing method for the conventional capacitance element. FIGS.
10
(
a
) to
10
(
e
) are cross-sectional views illustrating the process of manufacturing the conventional capacitance element.
First, in the step shown in FIG.
10
(
a
), a first platinum film
22
a
, a ferroelectric film
23
a
, and a second platinum film
24
a
are formed sequentially on the substrate
21
. Next, in the step shown in FIG.
10
(
b
), the second platinum film
24
a
is patterned by using a photoresist mask to form the upper electrode
24
. Next, in the step shown in FIG.
10
(
c
), the dielectric film
23
a
is patterned by using a photoresist mask covering a region including the upper electrode
24
to form the capacitance insulating film
23
having the aperture
25
. Furthermore, the first platinum film
22
a
is etched selectively by using a photoresist mask covering the upper electrode
24
, the capacitance insulating film
23
, and the aperture
25
to form the lower electrode
22
.
Next, in the step shown in FIG.
10
(
d
), the interlayer insulating film
26
is formed on the substrate, followed by the first contact hole
27
formed to extend through the interlayer insulating film
26
to reach the lower electrode
22
and the second contact hole
28
formed to extend through the interlayer insulating film
26
to reach the upper electrode
25
.
Next, in the step shown in FIG.
10
(
e
), the titanium film and the aluminum alloy film are deposited over the entire surface of the substrate. The titanium film and the aluminum alloy film are then patterned by using a photoresist mask covering the contact holes
27
and
28
and their surroundings to form the first electrode wire
29
to be connected to the lower electrode
22
and the second electrode wire
30
to be connected to the upper electrode
24
.
Although each of the first and second electrode wires
29
and
30
is shown as a single-layer film in FIG.
10
(
e
) for the sake of simplicity, it is typically composed of a multilayer film such as the two-layer film consisting of the aluminum alloy film and the titanium film or the three-layer film consisting of the aluminum alloy film, the titanium nitride film, and the titanium film as described above.
In the conventional capacitance element, excellent adhesion is required between the second electrode wire
30
and the upper electrode
24
. Moreover, since the capacitance insulating film
23
is typically composed of a ferroelectric material containing a metal oxide as a main component, the platinum film is used to compose each of the upper and lower electrodes
24
and
22
as a material which is unreactive to the metal oxide and capable of withstanding high temperature during thermal treatment. Furthermore, the titanium layer is interposed between the aluminum layer and the platinum layer to compose each of the electrode wires
29
and
30
due to poor adhesion between the aluminum layer and the platinum layer, thereby solidifying the connection between the electrode wires and the electrodes of the capacitance element.
To improve the performance of the capacitance element, thermal treatment is indispensably performed after the formation of the electrode wires
29
and
30
in the manufacturing process. After the heat treatment was performed with respect to the electrode wires
29
and
30
, however, the phenomenon was observed in which the performance of the ferroelectric film composing the capacitance insulating film
23
was degraded.
The cause of the degraded performance was tracked down and presumed as follows. The platinum film composing each of the upper and lower electrodes
24
and
22
of the capacitance element has a columnar crystal structure since it is normally formed by sputtering. During the thermal treatment performed with respect to the electrode wires
29
and
30
, titanium composing the lower layer of the second electrode wire
30
diffuses into the capacitance insulating film
23
through the grain boundary of the columnar crystal in the platinum film composing th
Judai Yuji
Mikawa Takumi
Nagano Yoshihisa
Keshavan B. V.
Matsushita Electric - Industrial Co., Ltd.
Smith Matthew
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