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
2001-01-08
2004-03-16
Clark, Sheila V.. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S758000
Reexamination Certificate
active
06707154
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having contact parts according to a self-alignment method and production method for the same.
2. Prior Art
The integration degree of semiconductor devices has increased in recent years while memory cells have been scaled down and, at the same time, it has become difficult to open contact holes between wires, by using solely a photoresist mask, without causing short circuiting from the wires. Therefore, a method called the self-alignment method is adopted as a method for opening contact holes without short circuiting the wires.
In the following, a structure of a conventional semiconductor device as well as its production method in the case that a self-alignment method is adopted are described in reference to FIG.
61
.
As shown in
FIG. 61
isolation regions
11
are selectively formed on the main surface of a semiconductor substrate
10
. Then a silicon oxide film
1
is formed on the main surface of the semiconductor substrate
10
and the wiring is formed thereon. The wires have a polycrystal silicon film
2
and a silicide film
3
.
On the wiring a nitride film (a hard mask film)
4
is formed. A silicon oxide film
5
is also formed on the side walls of the wires. At this time the oxidation rate of the silicide film
3
is faster than that of the polycrystal silicon film
2
and, therefore, the silicon oxide film
5
has a shape which locally projects to the side.
A nitride film
6
is formed so as to cover the silicon oxide film
5
and nitride film
4
. A silicon oxide film
7
is formed so as to cover this nitride film
6
and an interlayer oxide film
8
is formed so as to cover the silicon oxide film
7
.
Afterwards contact holes which reach to the main surface of the semiconductor substrate
10
are formed between the wires and conductive layers (plug parts) are formed within the contact holes.
In the above described prior art wherein a self-alignment method is adopted, however, a defective filling of the interlayer oxide film
8
can occur in the case that scaling down has further advanced so that the distance between wires becomes very short.
As for a primary cause of the defective filling of the interlayer oxide film
8
, firstly, the fact that the upper edge corner part of the wires as shown in
FIG. 61
are squared can be cited. Because of the existence of those squared parts the opening areas on the upper surface of the regions between the wires become smaller so as to cause the easy occurrence of a defective filling. The existence of the projecting parts on the side walls of the wires as shown in
FIG. 61
can also be a primary cause of defective fillings. In addition, the steepness of the side of the wires can be a primary cause of defective fillings.
The occurrence of the defective fillings of the interlayer oxide film
8
as described above causes a void
9
between the wires as shown in FIG.
61
. In the case that the void
9
has occurred in this way, a conductive layer is filled in, as well as into the void
9
, when plug parts are formed within the contact holes in the latter process. Thereby, the contact parts
24
are connected to each other with the conductive layer which is filled in within the void
9
as shown in
FIG. 62
, which leads to the problem that the plug parts are short circuited with each other. Here, in
FIG. 62
, active regions are denoted as
22
and wires are denoted as
23
.
The development of scaling down has been particularly remarkable in recent years and there is a tendency that the height of the wires have become larger in order to decrease the wiring resistance and, therefore, the situation of the above described problem is more and more prone to occur.
SUMMARY OF THE INVENTION
The present invention is provided to solve the above described problem. The purpose of the present invention is to prevent a short circuit between the plug parts due to defective fillings or the like of the interlayer insulation film between the wires.
A semiconductor device according to one aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with an insulation film interposed, a hard mask film on the wires, a nitride film having rounded upper edge corner parts covering the hard mask film, an interlayer insulation film covering the nitride film and plug parts formed within the interlayer insulation film. Here, in the present invention, the plug parts are referred to as conductive parts formed within the interlayer isolation film so as to connect conductive layers to each other. Accordingly, the plug parts according to the present invention may be formed as a part of wiring in one case and may be formed of a conductive material which is different from that of the wiring in another case.
By rounding the upper edge corner parts of the nitride film as described above, the opening areas of the upper surface of the regions between the wires can be increased in comparison to the case where the upper edge corner parts of the nitride film are not rounded. Thereby, defective fillings of the interlayer insulation film between the wires can be limited.
In the case that the width of the nitride film located on the above described hard mask film is denoted as L and the height from the bottom of the hard mask film to the top of the nitride film is denoted as H, it is preferable for the width a of the rounded part in the nitride film to be in the range of 0<a<L/2 and for the height b of the rounded part to be in the range of 0<b<H. Thereby, the opening areas of the regions between the wires can be effectively increased.
In addition, the hard mask film has, preferably, rounded upper edge corner parts. In this case the upper edge corner parts of the nitride film can be rounded so that the defective fillings of the interlayer insulation film between the wires can be limited.
In the case that the width of the hard mask film is denoted as L and the height is denoted as H it is preferable for the width a of the rounded upper edge corner parts in the hard mask film to be in the range of 0<a<L/2 and for the height b of the rounded parts to be in the range of 0<b<H. Thereby, the opening areas of the regions between the wires can be effectively increased.
A semiconductor device according to another aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with an insulation film interposed, a hard mask film on the wires, an oxide film formed on the side walls of the wires, a nitride film covering the hard mask film and the oxide film, an interlayer insulation film covering the nitride film and plug parts formed within the interlayer insulation film. Then the surface of the oxide film extends substantially in the direction perpendicular to the main surface of the semiconductor substrate without locally projecting to the side.
In this case, since the oxide film formed on the side walls of the wires does not protrude to the side, the defective fillings of the interlayer insulation film between the wires can be controlled in comparison to a prior art wherein the oxide film projects to the side.
The above described wires have a silicon film and a silicide film so that the side of the silicide film is located inward than the side of the silicon film. Then the shift amount of the side of the silicide film to the inner side of the wires from the side of the hard mask film is preferably ½ times or more and {fraction (3/2)} times or less as large as the thickness of the oxide film located on the side walls of the silicon film.
By properly adjusting the shift amount of the side of the silicide film in this way the surface of the oxide film can be prevented from locally projecting to the side so that the defective fillings of the interlayer insulation film between the wires can be limited.
A semiconductor device according to still another aspect of the present invention comprises a semiconductor substrate having a
Shimizu Masahiro
Terauchi Takashi
Clark Sheila V..
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
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