Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
1999-09-24
2003-04-01
Paladini, Albert W. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S618000, C257S622000, C257S377000, C257S774000, C257S773000, C257S623000, C257S759000, C257S764000, C257S700000, C438S586000, C438S589000, C438S638000, C438S639000, C438S640000, C438S675000, C438S629000, C438S637000
Reexamination Certificate
active
06541864
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device which has a particularly fine contact structure and which has been subjected to a high-density integration, and a method of manufacturing the same.
In a semiconductor device, an element area or an interwire contact structure obtained by contact holes are further made fine, and accuracy and low resistance contributing to high reliability are required.
FIGS. 12A
to
12
F are sectional views for explaining a first conventional example showing a method of manufacturing of a contact-wire structure in the order of manufacturing processes. This technique is illustrated, for example, with reference to Jpn. Pat Appln. Publication No. 9-172067 or the like, and it is a technique for forming wire grooves and contact holes in a self-aligning manner.
As shown in
FIG. 12A
, a wire layer
701
is formed in advance on a insulation film
700
by using a well-known technique such as a damascene method or the like, and an insulation film
702
such as a silicon oxide film is deposited on the insulation film
700
. Next, as shown in
FIG. 12B
, an insulation film
703
different in etching rate from the insulation film
702
, for example, a silicon nitride film or the like, is thin deposited on the insulation film
702
.
Next, as shown in
FIG. 12C
, opening portions
704
are formed on the insulation film
703
by using a photolithography technique and an etching technique. Next, as shown in
FIG. 12D
, an insulation film
705
different in etching rate from the insulation film
703
, for example the same silicon oxide film as the insulation film
702
or the like, is further deposited on the insulation film
703
.
Next, as shown in
FIG. 12E
, wire grooves
706
are formed on the insulation film
705
by using a lithography technique and an anisotropic selective etching technique. At this time, portions of the insulation film
702
corresponding to overlapping portions of a wire groove pattern and the opening portions
704
are also etched. Thereby, contact holes
707
are also formed simultaneously with formation of the wire grooves
706
. That is, it is possible to form the wire grooves
706
and the contact holes
707
in a self-aligning manner.
Next, as shown in
FIG. 12F
, conductive material
708
is embedded in the wire grooves
706
and the contact holes
707
, and projecting portions of the conductive material
708
are removed by using, for example, CMP (Chemical Mechanical Polishing) so that the conductive material
708
is flattened. Thereby, contact plugs
710
and wire layers
709
are formed.
According to the above configuration, contact hole positions are determined at overlapping portions of the opening portions
704
and the wire grooves
706
. When each wire groove
706
is formed wider in the vicinity of each contact hole position to securely accommodate each opening portion
704
at a time of formation of the wire grooves
706
, a problem of misalignment between the wire groove
706
and the contact hole
707
can be overcome.
Also, when there is an extra area in a contact area of the lowermost layer to some extent, the opening portion
704
may be formed wider in the vicinity of the contact hole position at least in a direction intersecting the wire groove
706
. The opening portion
704
can securely be accommodated in the wire groove
706
at a time of formation of the wire groove
706
so that the problem of misalignment between the wire groove
706
and the contact hole
707
can be overcome.
However, according to the first conventional example, the wire groove
706
and the contact hole
707
are formed by using an anisotropic selective etching technique. For this reason, side walls of the contact hole
707
are formed approximately vertically to a semiconductor substrate face.
FIGS. 13
,
14
A,
14
B,
15
,
16
A and
16
B are views showing problems regarding such a manufacturing method as the above first conventional example.
FIG. 13
is a plan view showing wire grooves and a contact hole,
FIGS. 14A and 14B
are sectional views taken along line XIVA—XIVA and XIVB—XIVB, respectively, and
FIG. 15
is a sectional view showing an aspect where conductive material is embedded in the contact hole in the sectional view of FIG.
14
A.
FIGS. 16A and 16B
are respectively sectional views corresponding to
FIGS. 14A and 14B
, for showing a modified example. Same reference numerals are attached to portions similar to the first conventional example shown in
FIGS. 12A
to
12
F.
In
FIGS. 13
,
14
A and
14
B, in an insulation film
703
defining a bottom portion of a wire groove, an opening portion
704
is formed wider in the vicinity of a contact hole position at least in a direction intersecting a wire groove
706
. A contact hole
707
is etched approximately vertically to the bottom portion. It is difficult to embed barrier metal or conductive material
708
in such a contact hole
707
in a preferable manner.
As shown in
FIG. 15
, for example, there is a drawback in which a seam
711
and a void
712
may occur. The seam
711
prevents planarization in a grinding process performed later. It is hard to foresee adverse influence of gas in the void
712
in a heating process performed later.
In view of the above, it is considered to employ a taper etching technique as a method for embedding conductive material
708
in the contact hole
707
in a preferable manner. That is, a taper angle is provided to a side wall of the contact hole
707
by controlling etching conditions. Thereby, an embedding characteristic of the conductive material
708
embedded in the contact hole
707
is improved.
FIGS. 16A and 16B
are sectional view corresponding to
FIGS. 14A and 14B
, where the taper etching technique is adopted. That is,
FIGS. 16A and 16B
show a structure obtained by employing the taper etching technique in order to form wire grooves
706
and contact holes
707
simultaneously.
As shown in
FIG. 16A
, in a section taken along a direction of the wire groove
706
, a taper angle is provided to each contact hole side wall by a method using the taper etching technique so that improvement in embedding characteristic is expected. It should be noted that, when an area (an area contacting with conductive material) of a contact hole bottom face
715
is intended to be secured to some extent, an opening area at an upper portion of the contact hole
707
is larger than the area of the contact hole bottom face
715
.
As shown in
FIG. 16B
, a section taken along a direction perpendicular to the wire groove
706
clearly illustrates a harmful influence due to using the taper etching technique. When the area (an area contacting with conductive material) of the contact hole bottom face
715
intended to be secured to some extent, the opening area of the upper portion of the contact hole
707
becomes larger than the area of the bottom face.
As mentioned above, as the contact holes
707
and the wire grooves
706
are simultaneously formed, all the wire grooves
706
are tapered. Accordingly, an interval between adjacent wire grooves
706
at their upper portions is made small, so that a possibility where a short-circuit may occur between wire layers is increased.
Namely, the wire groove
706
itself has an aspect ratio smaller than that of the contact hole portion, and the taper angle is not so required at the side wall of the wire groove. However, the side wall of the wire groove
706
is necessarily provided with a taper angle when the method for forming the wire grooves
706
and the contact holes
707
simultaneously is used. As shown with Db in
FIG. 16B
, a configuration where the adjacent wire grooves are unnecessarily close to each other prevents the wire region or area from being structured further fine.
On the other hand, attention is paid to the contact structure itself in the contact hole. As a fine structurization advances, contact resistance, reaction barrier performance and covering characteristic for serving as an embedded plug become important. A conventional example will be explained
Banner & Witcoff , Ltd.
Kabushiki Kaisha Toshiba
Mitchell James
Paladini Albert W.
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