Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-12-31
2004-11-30
Blum, David S. (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S639000
Reexamination Certificate
active
06825112
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to semiconductor devices and methods of production thereof, and more particularly to semiconductor devices having contact holes and methods of production thereof.
BACKGROUND OF THE INVENTION
Semiconductor integrated circuits continue to become more highly integrated. As integration increases, the size of integrated circuit elements, for example transistors, can become increasingly small. As elements become smaller, the spacing between adjacent elements, such as conductive lines or “wires,” can become smaller too. Smaller spacing constraints can result in decreased spacing margins for a contact hole that is to be formed between and/or adjacent to wires. This will be explained with reference to
FIGS. 12 and 13
.
FIGS. 12 and 13
illustrate spacing margins for two examples of a contact hole
1200
. The contact hole
1200
is formed in two interlayer insulating films, shown as
1202
and
1204
, and can expose a diffusion layer
1206
. Wires, shown as
1208
, are formed between the interlayer insulating layers (
1202
and
1204
), and a contact hole
1200
is formed between the wires
1208
.
It is noted that
FIG. 12
illustrates a contact hole
1200
having a smaller diameter than the contact
1200
of FIG.
13
.
Typically, the formation of a contact hole
1200
can include certain minimum requirements. First, the diffusion layer
1206
should be sufficiently exposed to allow contact with the diffusion layer
1206
. Second, wires
1208
should be sufficiently isolated from an electroconductive layer (not shown) that is to be deposited into the contact hole
1200
. Ideally, such requirements meet particular absolute values. In reality, however, due to process and other variations, a certain amount of variation is typically accounted for in order to meet such requirements in a practical sense.
FIGS. 12 and 13
include particular measurements. Measurement “a1” represents the exposed area of diffusion layer
1206
. Measurement “b1” represents the distance between the wall of the contact hole
1200
and a wire
1208
. It is desirable to have a large “a1,” value, because a larger exposed area of a diffusion layer can lead to lower contact resistance. One skilled in the art would recognize that lower contact resistance can lead to faster and/or lower power semiconductor devices. Of course, if the value a
1
was zero, it would fail the requirements described above. Typically, a value a
1
must meet a minimum value, or have a certain margin to account for variations in the size of features introduced by the fabrication process.
It is also desirable to have a large “b1” value. The larger the value of “b1,” the larger the distance between the internal wall of contact
1200
and wire
1208
. A larger such distance “b1” can result in reduced risk of a short-circuit condition (short) between an electroconductive layer formed in the contact hole
1200
(not shown) and a wire
1208
. A shorter such distance “b1” can result in an increased risk of a short between an electroconductive layer (not shown) and a wire
1208
. Such an increased risk is not desirable. Of course, if b
1
was zero, it would fail the requirements described above. As in the case of the value a
1
, the value b
1
must typically meet a minimum value, or have a certain margin to account for variations in the size of features introduced by variations in the fabrication process.
Meeting the various requirements of a contact can be complicated because, as shown in
FIGS. 12 and 13
, the values a
1
and b
1
have a “trade-off” relationship with respect to one another. In particular, if the value b
1
(i.e., the distance between the internal wall of contact hole
1200
and a wire
1208
) is made larger, the resulting a
1
value (i.e., the exposed area of diffusion layer
1206
) can be smaller. This relationship is shown in FIG.
12
. Conversely, if the value a
1
(i.e., the exposed area of diffusion layer
1206
) is made larger, the resulting value b
1
(i.e., the distance between the internal wall of contact hole
1200
and a wire
1208
) can be smaller. This relationship is shown in FIG.
13
.
FIGS. 14 and 15
show profiles of a semiconductor device after an electroconductive layer
1210
is deposited into a contact hole
1200
.
FIGS. 14 and 15
can be considered to correspond to
FIGS. 12 and 13
, respectively.
A number of countermeasures have been proposed to further prevent a short between an electroconductive layer deposited in a contact hole and an adjacent wire. Such countermeasures include a side-wall contact structure or tapered contact structure. The examples of
FIGS. 12-15
set forth examples of a side-wall contact structure and a tapered contact structure. Accordingly, a side-wall contact structure and a tapered contact structure will now be described with reference to
FIGS. 12-15
.
A side-wall contact structure includes a side-wall insulating film formed on the internal wall of a contact hole
1200
, and is shown in
FIGS. 12-15
as item
1212
. In such a structure, if a contact hole
1200
was formed in such a way that it would result in a value b
1
of zero (namely, opening the contact hole
1200
would expose a wire
1208
) side-wall
1212
could serve to intervene between a wire
1208
and an electroconductive layer
1210
deposited into a contact hole
1200
, preventing a short between the two. The side-wall contact structure is shown in Japanese Patent Application Laid-Open No. 10-144788.
In a tapered contact structure, the internal wall of a contact hole
1200
is not vertical, but inclined. Consequently, the closer the contact hole
1200
is to the bottom, the smaller the area of the contact. This is illustrated in
FIGS. 12-15
, which show contact holes
1200
that are larger toward the top than toward the bottom. Consequently, because the tapered contact has a smaller area as it proceeds deeper toward the bottom of the contact, the distance b
1
(between the wall of the hole
1200
and wire
1208
) can be larger than the case where a contact hole is essentially cylindrical. This can lead to increased spacing margins and/or increase the resulting boundary between the internal wall of a contact hole and an adjacent wire.
In the conventional cases described above, side-wall contact structures and tapered contact structures can be employed to prevent shorts between an electroconductive layer
1210
and a wire
1208
. Unfortunately, both structures tend to reduce the resulting exposed area a
1
of the diffusion layer
1206
.
In more detail, in the case of the side-wall contact structure, the resulting side-wall
1212
can cover the diffusion layer
1206
. In particular, the exposed diffusion layer
1206
is covered by the thickness of side-wall
1212
on all sides.
In the case of the tapered contact structure, the internal wall of a contact hole
1200
has an inclined surface. Obviously, as the internal surface is inclined, the resulting exposed area of diffusion region
1206
becomes smaller.
As can be seen from the above description, while the employment of a side-wall contact structure and/or a tapered contact structure can be effective in reducing shorts between an electroconductive layer
1210
and an adjacent wire
1208
, such approaches can also be accompanied by corresponding reductions in the exposed area a
1
of the diffusion layer
1206
. As noted above, this can lead to undesirable increases in contact resistance.
In light of the above drawbacks in conventional approaches, it would be desirable to arrive at a semiconductor structure, and method of production thereof, that can prevent shorts between an electroconductive layer
1210
and an adjacent wire
1208
, while at the same time exposing a larger portion of a diffusion layer.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, a semiconductor device can include an interlayer insulating film formed over a semiconductor substrate that includes a contact hole formed therein. A side-wall film can cover a portion of the internal surface of the contact hole. An electr
Blum David S.
NEC Corporation
Sako Bradley T.
Walker Darryl G.
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