Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – Insulated gate formation
Reexamination Certificate
2000-10-25
2003-07-29
Pham, Long (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
Insulated gate formation
C438S308000, C438S584000, C438S585000, C438S586000
Reexamination Certificate
active
06599820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a method of producing the semiconductor device, in particular, a method of producing a semiconductor device having a polymetal wiring made of a polycrystalline silicon, an reaction preventing film, and a polymetal wire made of tungsten, especially used for forming highly heat-resistant wire such as a gate electrode.
2. Discussion of Background
In recent years, in accordance with microminiaturization, high integration, and high speed of semiconductor devices, a development of wiring materials having a further small resistance is required. As a wiring material used at portions requiring heat resistance, e.g. a gate electrode of a transistor, instead of a polycide structure fabricated by a polycrystalline silicon film and a metallic silicide film having a high-melting point, a tungsten film being one of high-melting point metals, a polycrystalline silicon film, or polymetal wiring made of a silicide reaction preventing film including a tungsten film and a polycrystalline silicon film. This is because the polymetal wiring using the tungsten film is hoped as wiring having a low sheet resistance in comparison with polycide wiring without an increment of the height of a gate.
FIGS. 11
a
through
13
are cross-sectional views illustrating steps of a method of producing a conventional p-type MOS transistor having a gate electrode made of polymetal wiring. As illustrated in
FIG. 11
a
, an element isolation insulating film
2
is formed on a silicon substrate
1
to separate an element forming region.
In the next, as illustrated in
FIG. 11
b
, a gate oxide film
3
is formed on an entire surface of the silicon substrate
1
.
In the next, as illustrated in
FIG. 11
c
, a polycrystalline silicon film
4
is formed on an entire surface, and BF
2
is subjected to ion implantation to form gate wiring of a p-type.
In the next, as illustrated in
FIG. 11
d
, a titanium nitride film
5
is formed on an entire surface of the polycrystalline silicon film
4
by a reactive sputtering method using a metallic target such as Ti. This titanium nitride
5
is served as a reaction preventing film preventing a reaction between the polycrystalline silicon film
4
and a tungsten film to be formed later.
In the next, as illustrated in
FIG. 11
e
, the tungsten film
6
is formed on an entire surface of the titanium nitride film
5
by a CVD method reducing tungsten hexafluoride by monosilane and hydrogen.
As illustrated in
FIG. 12
a
, thee tungsten film
6
, the titanium nitride film
5
, the polycrystalline silicon film
4
, and the gate oxide film
3
are simultaneously patterned to form a gate electrode
7
using a resist (not shown) as a mask.
In the next, as illustrated in
FIG. 12
b
, after forming side walls
8
on both sides of the gate electrode
7
, BF
2
is implanted in source/drain areas of the silicon substrate on both sides of the side walls
8
to form a p-type impurity diffusing layer
9
, and is subjected to annealing at 800 through 1,000° C. for activation.
In the next, as illustrated in
FIG. 12
c
, an inter-layer insulating film
10
made of an SiN film, a PSG film, and a BPSG film is formed on an entire surface. Thereafter, when the PSG film and/or the BPSG film are used, a thermal treatment at 800 through 1,000° C. is performed. This thermal treatment is an indispensable step because a quality of the inter-layer insulating film
10
is improved and planarized.
In the next, as illustrated in
FIG. 12
d
, a contact hole
11
is opened at a predetermined position on the gate electrode
7
and the impurity diffusing layer
9
. Further, there is a case that BF
2
being an impurity of a type same as that of the impurity diffusing layer
9
is implanted in the semiconductor substrate from an opening portion of the contact hole
11
, and the impurity is diffused by a thermal treatment at 800 through 1,000° C.
Finally, as illustrated in
FIG. 13
, a metallic wire
12
made of aluminum and so on is formed, whereby a transistor having the gate electrode
7
, fabricated by the tungsten film
6
, the titanium nitride
5
being the reaction preventing film, and the polycrystalline silicon film
4
, is completed.
The method of producing the conventional p-type MOS transistor using the polymetal wiring as the gate electrode wiring is as described. As illustrated in
FIGS. 12
b
,
12
c
, and
12
d
, the impurity diffusing layer
9
is activated as described, wherein the thermal treatment process at 800 through 1,000° C. is indispensable in order to improve the quality of the inter-layer insulating film
10
and planarizing the inter-layer insulating film
10
.
Further, in the method of producing the conventional p-type MOS transistor, fluorine is taken in the polymetal wiring film in the following steps of the production.
(1) As illustrated in
FIG. 11
c
, fluorine contained in the BF
2
implanted in the polycrystalline silicon film
4
for forming the gate wiring of a p-type.
(2) As illustrated in
FIG. 11
e
, fluorine contained in the tungsten hexafluoride used at time of forming the tungsten film
6
by the CVD method.
(3) As illustrated in
FIGS. 12
b
and
12
d
, fluorine contained in BF
2
implanted in the silicon substrate
1
and the tungsten film
6
at time of ion-implanting BF
2
for forming the p-type impurity diffusing layer
9
.
By the thermal treatment of fluorine taken in the polymetal wiring film, fluorine diffuses toward an interface between the polycrystalline silicon film
4
and the tungsten film
6
of the polymetal wiring, whereby a contact between the polycrystalline silicon film
4
and the tungsten film
6
is deteriorated. As a result, there is a problem that the polycrystalline silicon film
4
and the tungsten film
6
are separated at an interface therebetween during or after the thermal treatment or by stresses of the inter-layer insulating film
10
and of a film of metallic wiring
12
.
Further, fluorine in the polymetal wiring diffuses and reaches the gate oxide film
3
by the thermal treatment, whereby an effective capacitance of the gate oxide film
3
increases. As a result, the effective film thickness of the gate oxide film is larger than a designed value, whereby there is a problem that a property of a transistor is deteriorated.
SUMMARY OF THE INVENTION
The present invention is provided to solve the above-mentioned problems inherent in the conventional techniques, and to provide a method of producing a semiconductor device having a polymetal wiring structure, by which a content of fluorine can be reduced, a film separation is prevented, and a preferable transistor property is obtainable.
According to a first aspect of the present invention, there is provided a method of producing a semiconductor device, wherein a tungsten film is formed by a sputtering method, and a content of fluorine in a target, used in the sputtering method, is 10 ppm or less.
According to a second aspect of the present invention, there is provided a method of producing a semiconductor device, wherein a tungsten film is formed by a sputtering method, and a temperature of a silicon substrate, formed by the sputtering method, is maintained to be 200° C. or more.
According to a third aspect of the present invention, there is provided a method of producing a semiconductor device comprising a step of annealing the semiconductor device at 600° C. or more after ion-implanting BF
2
in a polycrystalline silicon film and before forming a reaction preventing film.
According to a fourth aspect of the present invention, there is provided a method of producing a semiconductor device, wherein a step of annealing is conducted in a vacuum for a reactive atmosphere for fluorine.
According to a fifth aspect of the present invention, there is provided a method of producing a semiconductor device comprising steps of sequentially forming a gate oxide film, a polycrystalline silicon film, a reaction preventing film, and a tungsten film on a silicon substrate; forming a silicon nitride film on th
Kanda Yasuhiro
Kimoto Mitsuo
Maekawa Kazuyoshi
Sekiguchi Noboru
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Pham Long
LandOfFree
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