Semiconductor device with improved interconnection

Details Semiconductor device with improved interconnection Semiconductor device with improved interconnection

1998-04-21

2001-01-16

Tran, Minh Loan (Department: 2811)

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

Combined with electrical contact or lead

Of specified material other than unalloyed aluminum

C257S751000, C257S754000, C257S757000, C257S763000, C257S770000, C257S750000, C257S760000, C438S627000, C438S629000, C438S630000, C438S643000, C438S647000, C438S648000

Reexamination Certificate

active

06175156

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a semiconductor device, and more particularly to an improved semiconductor device having an interconnection (wiring) layer and being capable of preventing a short-circuit between the wiring layer and another wiring layer with different potential or between the wiring layer and a semiconductor substrate.
2. Description of the Background Art
FIG. 3
is a sectional view of a semiconductor device such as a semiconductor memory device having a conventional structure of multilayer interconnection.
Referring to
FIG. 3
, an interlayer insulating film
5
a
is formed on a semiconductor substrate
1
. A first conducting layer
2
is formed on interlayer insulating film
5
a
. An interlayer insulating film
5
b
is formed on interlayer insulating film
5
a
such that it covers first conducting layer
2
. A second conducting layer
3
is formed on interlayer insulating film
5
b
. An interlayer insulating film
5
c
is formed on interlayer insulating film
5
b
such that it covers second conducting layer
3
. A contact hole
6
a
is formed in interlayer insulating films
5
a
,
5
b
, and
5
c
in order to expose the surface of semiconductor substrate
1
. A contact hole
6
b
is formed in interlayer insulating film
5
c
in order to expose the surface of second conducting layer
3
. Contact hole
6
b
penetrates second conducting layer
3
, interlayer insulating film
5
b
, and interlayer insulating film
5
a
, reaching the surface of semiconductor substrate
1
. A contact hole
6
c
is formed in interlayer insulating films
5
b
and
5
c
in order to expose the surface of first conducting layer
2
. A third conducting layer
4
a
is formed on interlayer insulating film
5
c
such that it is connected to the surface of semiconductor substrate
1
through contact hole
6
a
. A third conducting layer
4
b
is formed on interlayer insulating film
5
c
such that it is connected to second conducting layer
3
through contact hole
6
b
. Third conducting layer
4
b
is connected to first conducting layer
2
through contact hole
6
c
.
Referring to
FIG. 3
, in a conventional semiconductor device, conducting layers are connected to each other through contact holes formed in an interlayer insulating film to connect two conducting layers formed across different layers.
As shown in
FIG. 3
, however, the total thickness of interlayer insulating films
5
a
,
5
b
and
5
c
formed between third conducting layer
4
a
and semiconductor substrate
1
, the thickness of interlayer insulating film
5
c
formed between third conducting layer
4
b
and second conducting layer
3
, and the thickness of interlayer insulating films
5
b
and
5
c
formed between third conducting layer
4
b
and first conducting layer
2
are different. Therefore, when contact holes
6
a
,
6
b
and
6
c
are formed simultaneously, contact hole
6
b
penetrates second conducting layer
3
and reaches the surface of semiconductor substrate
1
, by the etching to form contact hole
6
a
reaching the surface of semiconductor substrate
1
.
Such a penetration occurs when etching selectivity of second conducting layer
3
to interlayer insulating film
5
c
is small. In other words, penetration of second conducting layer
3
occurs when the difference between the etching rate of second conducting layer
3
and the etching rate of interlayer insulating film
5
a
,
5
b
,
5
c
is small. For example, the etching selectivity of interlayer insulating film
5
c
to materials such as polysilicon and doped polysilicon is small.
Thus, in the conventional device, when second conducting layer
3
is formed of a material of small etching selectivity to interlayer insulating film
5
c
, contact hole
6
b
penetrates second conducting layer
3
. As a result, a short circuit is formed between one wiring layer and another wiring layer with different potential or between a wiring layer and a semiconductor substrate.
SUMMARY OF THE INVENTION
The present invention was made to solve the problems described above. An object of the invention is to provide an improved semiconductor device which prevents a short circuit as described above.
The invention according to an aspect relates to a semiconductor device having an upper conducting layer and a lower conducting layer connected via a contact hole. The semiconductor device includes a semiconductor substrate having a surface. A first interlayer insulating film is formed on the semiconductor substrate. The lower conducting layer is formed on the first interlayer insulating film. A second interlayer insulating film is formed on the first interlayer insulating film such that it covers the lower conducting layer. An upper conducting layer is formed on the second interlayer insulating film. A contact hole is formed in the second interlayer insulating film in order to connect the upper conducting layer and the lower conducting layer. A stopper layer of silicide or metal is formed directly below the contact hole between the surface of the semiconductor substrate and the lower conducting layer.
In accordance with the present invention, because of the stopper layer of silicide or metal formed directly below the contact hole between the surface of the semiconductor substrate and the lower conducting layer, even if the contact hole penetrates the lower conducting layer, further penetration can be prevented.
In a semiconductor device according to another aspect, the etching selectivity of a second interlayer insulating film to a stopper layer becomes high because the stopper layer is formed of WSi.
In a semiconductor device according to a further aspect, a stopper layer is formed of TiSi. Therefore the etching selectivity of a second interlayer insulating film to the stopper layer becomes high.
In a semiconductor device according to a still further aspect, a stopper layer includes two layers, one of WSi and another of polysilicon. Therefore the etching selectivity of a second interlayer insulating film to the stopper layer becomes high.
In a semiconductor device according to a still further aspect, a stopper layer is at the same potential as an upper conducting layer. Therefore, short circuits can be prevented even if a contact hole penetrates a lower conducting layer and reaches the stopper layer.
In a semiconductor device according to a still further aspect, a stopper layer is set to a floating state. Therefore, short circuits would not be formed even if a contact hole penetrates a lower conducting layer and reaches the stopper layer.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 4648937 (1987-03-01), Ogura et al.
patent: 4833519 (1989-05-01), Kawano et al.
patent: 5027185 (1991-06-01), Liauh
patent: 5036382 (1991-07-01), Yamaha
patent: 5404046 (1995-04-01), Matsumoto et al.
patent: 5578518 (1996-11-01), Koike et al.
patent: 5739587 (1998-04-01), Sato
patent: 6015326 (2000-01-01), Potter
patent: 01120037A (1989-05-01), None
patent: 1-120037 (1989-05-01), None
Stanley Wolf and Richard N. Tauber, Silicon Processing for the VLSI Era, vol. 1: Process Technology, p. 397, 1986.

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