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
2000-03-10
2002-07-09
Quach, T. N. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S763000, C257S784000
Reexamination Certificate
active
06417568
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor devise having an improved structure of a bonding pad, and in particular to a semiconductor device comprising, as an interlayer insulating film, a BPSG film (an oxide film containing boron and phosphorus), and comprising a Ti film and a TiN film beneath a bonding pad film.
2. Description of the Related Art
FIG. 1
is a sectional view of a conventional bonding pad. A field oxide film
22
is deposited on a silicon substrate
21
to have a thickness of about 3000 Å. The field oxide film
22
is covered with a BPSG film
24
, as an interlayer insulating film, of about 4000 Å in thickness. A TiN/Ti film
27
(a lamination layer of a TiN film as an upper layer and a Ti film as a lower layer) of about 2000 Å in thickness is deposited on a bonding pad forming area of the BPSG film
24
. An aluminum film
28
of about 8000 Å in thickness is deposited as a bonding pad on the TiN/Ti film
27
. An opening is made in a cover film
29
formed on the whole surface in the manner that a part of each of the bonding areas of the aluminum film
28
is exposed.
In this manner, in the sectional structure of the conventional bonding pad, the BPSG film
24
directly contacts the Ti film of the TiN/Ti film
27
. For this reason, the conventional bonding pad has a drawback that the aluminum film
28
is easily peeled off when the pad is subjected to ball bonding to the Al film
28
.
The peeling off of the aluminum film
28
of the bonding pad by the ball bonding becomes still more remarkable as the buffering effect of the aluminum film
28
itself against the stress at the time of the bonding becomes smaller by making the aluminum film
28
thinner. In order to make the width of aluminum wiring finer, it is necessary to make the aluminum film thinner. However, easy peeling-off of the aluminum film
28
upon the ball bonding is a factor of hindering the width of the aluminum wiring from being made finer. In other words, in order to realize a finer wiring width by working the aluminum film by plasma etching, it is necessary to make a resist film, which is, an etching mask material, thinner. This is for the purpose of improving the resolution of the resist film. In this case, the etching rate of the resist film that is the etching mask material to the aluminum film to be etched is small. At the time of plasmaetching the aluminum film, therefore, in order not to etch all of the resist film that has been made thinner, it is necessary that by making the aluminum film thinner, the time required for etching the aluminum film is shortened. If the aluminum film attempts to be made thinner, the film is easily peeled off in this way upon bonding. After all, it is difficult to make the width of the aluminum wiring thinner.
Thus, in order to prevent the aluminum film of such a bonding pad from being peeled off, the Patent Gazette No. 2550248 suggests a sectional structure of a bonding pad shown in FIG.
2
. That is, a field oxide film
32
is deposited on a silicon substrate
31
. A polycide film
33
that is a lamination layer made of a tungsten silicide film
33
b
as an upper layer and a polycrystal silicon film
33
a
as a lower layer is formed in bonding pad forming area on the field oxide film
32
. A BPSG film
34
that is an interlayer insulating film is made to cover the field oxide film
32
and the polycide film
33
. A large number of contact holes
35
are made in the BPSG film
34
to reach the polycide film
33
. Tungsten is embedded as plugs in the contact holes
35
to form tungsten plugs
36
.
A TiN/Ti film
37
(a lamination film of a TiN film as an upper layer and a Ti film as a lower layer) is formed on the tungsten plugs
36
embedded in the contact holes
35
and the BPSG film
34
that is present in the bonding pad forming areas. An aluminum film
38
is formed as bonding pads on the TiN/Ti film
37
. Each of openings is made in a cover film
39
formed on the whole surface in the manner that a part of each of the bonding areas of the aluminum film
38
is exposed.
As described above, in the semiconductor device described in the above-mentioned Gazette, the tungsten plugs
36
are directly embedded in the contact holes
35
and subsequently the Tin/Ti film
37
is formed. Therefore, the Ti film as the lower layer of the TiN/Ti film
37
is brought into contact with not only the BPSG film
34
but also the tungsten plugs
36
. For this reason, the contact area of the Ti film as the lower layer of the TiN/Ti film
37
and the BPSG film
34
is reduced to a value lower than the value by conventional semiconductor devices. Thus, the aluminum film
38
is not easily peeled off.
However, in the conventional semiconductor device described in the above-mentioned Gazette, tungsten that is a plug material for contacts is directly embedded in the contact holes
35
. In element areas inside the semiconductor device, therefore, an impurity diffusion layer, which is formed in the silicon substrate, and tungsten are directly brought into contact with each other in the connection portion of the impurity diffusion layer and the aluminum wiring. Ti has the smallest resistance of contact with silicon among all metals. Accordingly, the contact resistance is larger in the case that the impurity diffusion layer is brought into contact with tungsten than in the case that the impurity diffusion layer is brought into contact with the Ti film. As a result, in the former case the properties and performances of the semiconductor device deteriorate.
Tungsten has the property that it does not adhere easily onto any insulating film. Therefore, if the tungsten plugs
36
are directly embedded in the contact holes
35
, the embedded tungsten may be peeled off from the BPSG film on side walls of the contact holes
35
. Such relationship between the BPSG film on the side walls of the contact holes and the tungsten is also true for contact holes made in the element area inside the semiconductor device. There is therefore a problem that is not favorite for reliability of the device.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a semiconductor (device making it possible to surely prevent an aluminum film which constitutes a bonding pad from being peeled off.
The semiconductor device according to the present invention comprises a semiconductor substrate, a polycide film selectively formed in a bonding area on the semiconductor substrate, an interlayer insulating film that is formed on the semiconductor substrate and comprises boron, a bonding pad film arranged on the polycide film, and a film of titanium ants a titanium compound that is formed between the polycide film and the bonding pad film to contact the polycide film and the bonding pad film.
This semiconductor device may have a structure wherein a plurality of contact holes are made in the interlayer insulating film on the polycide film, the holes penetrating the interlayer insulating film, and further the film of the titanium and the titanium compound is formed between the bonding pad film and the interlayer insulating film, and on bottom faces and side faces of the contact holes.
This semiconductor device may have a structure wherein an opening is made, on the polycide film, in the interlayer insulating film and the polycide film contacts the film of the titanium and the titanium compound continuously inside the bonding area.
The above-mentioned bonding pad film comprises, for example, an aluminum film. The above-mentioned polycide film is, for example, a lamination film that comprises an upper film comprising a substance selected from the group consisting of high melting-point metals, silicide thereof and nitride thereof, and a lower film comprising a polysilicon film. A field oxide film is formed between the silicon substrate and the polycide film.
As described above, according to the present invention, the TiN/Ti film is arranged between the aluminum film which makes the bonding pad and the polycide film beneath it
NEC Corporation
Quach T. N.
Sughrue & Mion, PLLC
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