Electrode and a capacitor and DRAM containing the same

Details Electrode and a capacitor and DRAM containing the same Electrode and a capacitor and DRAM containing the same

1999-11-05

2002-11-12

Loke, Steven (Department: 2811)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S306000

Reexamination Certificate

active

06479856

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode structure of capacitor, and more particularly to an electrode structure of capacitor using materials of high dielectric constant.
2. Description of the Background Art
Studies on dielectric of high dielectric constant have been conventionally made in order to increase capacitance of a capacitor in highly-integrated DRAM. For example, barium strontium titanate ((Ba
b
Sr
1-b
)TiO3:0<b<1, hereinafter referred to as “BST”) is introduced in Japanese Patent Application Laid Open Gazette No. 10-256503.
FIG. 20
is a cross section showing an exemplary structure of DRAM. In an upper surface of a semiconductor substrate
31
, an isolation oxide film
33
and an isolation impurity layer
35
are formed, and in a region of the upper surface of the semiconductor substrate
31
sectioned by these constituents, three impurity layers
25
are formed. The center impurity layer
25
is shared by a pair of MIS transistors
30
and the right and left impurity layers
25
are in contact with contact plugs
26
a.
Each MIS transistor
30
has a gate insulating film
21
, a gate electrode
23
formed on the gate insulating film
21
and an insulating film
27
covering the gate electrode
23
. Between a pair of insulating films
27
, a bit line
37
connected to the center impurity layer
25
is provided. The insulating films
27
and the bit line
37
are covered with an interlayer insulating film
24
a
while the contact plugs
26
a
penetrate the interlayer insulating film
24
a
to come into contact with barrier layers
61
a
. Upper and side surfaces of the barrier layer
61
a
are covered with lower electrodes
62
a
and
63
a
mainly made of platinum, which are further covered with a high-permittivity layer
64
(i.e., dielectric layer with high permittivity) made of BST. The high-permittivity layer
64
is covered with an upper electrode
81
mainly made of platinum, and the upper electrode
81
is further covered with a conductive film
10
. The conductive film
10
is covered with an interlayer insulating film
41
.
The lower electrodes
62
a
and
63
a
, the upper electrode
81
and the high-permittivity layer
64
constitute a capacitor, and one electrode of the capacitor is connected to the bit line
37
through the barrier layer
61
a
, the contact plug
26
a
and the transistor
30
.
On the other hand, the interlayer insulating film
41
is locally removed, and a layered structure consisting of a barrier layer
42
and an aluminum wire
43
is connected to the conductive layer
10
. Therefore, the other electrode of the capacitor is connected to the aluminum wire
43
through the upper electrode
81
, the conductive layer
10
and the barrier layer
42
.
FIG. 21
is a cross section showing constituents of the conductive layer
10
and connection between the conductive layer
10
and the layered structure of the barrier layer
42
and the aluminum wire
43
. The conductive layer
10
has a layered structure consisting of a barrier layer
10
a
, a stopper layer
10
b
and an adhesion layer
10
c
in this order from the near side of the upper electrode
81
. In some cases, the barrier layer
42
penetrates the adhesion layer
10
c
as shown in this figure due to overetching in anisotropic etching on the interlayer insulating film
41
to provide a trench for placing the aluminum wire
43
. The barrier layer
10
a
is made of, e.g., TiN to suppress a reaction in a heat treatment on the aluminum wire
43
and the upper electrode
81
. Further, the stopper layer
10
b
is made of PtSi since it works as a sacrifice reacting film when the aluminum wire
43
and the upper electrode
81
are reacted in the heat treatment. The stopper layer
10
b
also works to suppress the overetching when the interlayer insulating film
41
is anisotropically etched to provide a trench for placing the aluminum wire
43
. The adhesion layer
10
c
is formed to improve adhesion between the conductive film
10
and the interlayer insulating film
41
and, for example, made of TiN when the interlayer insulating film
41
is a silicon oxide. The structure of
FIG. 21
is shown, for example, in Japanese Patent Application Laid Open Gazette No. 10-256503.
In the above structure, however, the capability of the barrier layer
10
a
as a barrier is not perfect, and a reaction may be caused between the PtSi of the stopper layer
10
b
and Pt of the upper electrode
81
. With such a reaction, the BST may be reduced in an interface between the upper electrode
81
and the high-permittivity layer
64
. Further, depositing the conductive film
10
and the upper electrode
81
thereon puts a stress on the high-permittivity layer
64
.
SUMMARY OF THE INVENTION
The present invention is directed to an electrode structure of capacitor. According to a first aspect of the present invention, the electrode structure of capacitor has a first electrode layer; and a second electrode layer including platinum, silicon and at least one of oxygen and nitrogen, in this order from the side in contact with a dielectric layer of the capacitor.
Preferably, the second electrode layer has a higher composition ratio of at least one of oxygen and nitrogen on the near side from the first electrode layer than on the far side thereof.
According to a second aspect of the present invention, in the electrode structure of the first aspect, the second electrode layer has a double-layered structure, consisting of a third electrode layer located on the near side of the first electrode layer and a fourth electrode layer located on the far side thereof, and the third electrode layer has a higher composition ratio of at least one of oxygen and nitrogen than the fourth electrode layer.
According to a third aspect of the present invention, in the electrode structure of the second aspect, the fourth electrode layer also works as an adhesion layer.
According to a fourth aspect of the present invention, in the electrode structure of any one of the first to third aspects, platinum oxide is used for the first electrode layer.
Preferably, the dielectric layer is made of dielectric oxide.
The present invention is also directed to a capacitor. According to a fifth aspect of the present invention, the capacitor comprises: a dielectric layer; a first electrode layer formed on the dielectric layer; and a second electrode layer formed on the first electrode layer, including platinum, silicon and at least one of oxygen and nitrogen.
Preferably, the second electrode layer has a higher composition ratio of at least one of oxygen and nitrogen on the near side from the first electrode layer than on the far side thereof.
According to a sixth aspect of the present invention, in the capacitor of the fifth aspect, the second electrode layer has a double-layered structure, consisting of a third electrode layer located on the near side of the first electrode layer and a fourth electrode layer located on the far side thereof, and the third electrode layer has a higher composition ratio of at least one of oxygen and nitrogen than the fourth electrode layer.
According to a seventh aspect of the present invention, in the capacitor of the sixth aspect, the fourth electrode layer also works as an adhesion layer.
According to an eighth aspect of the present invention, in the capacitor of any one of the fifth to seventh aspects, platinum oxide is used for the first electrode layer.
Preferably, the dielectric layer is made of dielectric oxide.
The present invention is further directed to a DRAM. According to a ninth aspect of the present invention, the DRAM comprises: a capacitor having a dielectric layer, a first electrode layer formed on the dielectric layer, and a second electrode layer formed on the first electrode layer, including platinum, silicon and at least one of oxygen and nitrogen.
Preferably, the second electrode layer has a higher composition ratio of at least one of oxygen and nitrogen on the near side from the first electrode layer than on the far side thereof.
According to a

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