Method for producing semiconductor device

Details Method for producing semiconductor device Method for producing semiconductor device

2001-03-20

2003-05-20

Niebling, John F. (Department: 2812)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S655000

Reexamination Certificate

active

06566257

ABSTRACT:

CROSS-REFERENCES TO RELATED APPLICATION
This application is related to Japanese Patent Application No. 2000-124311, filed on Apr. 25, 2000 whose priority is claimed under 35 USC §119, the disclosures of which are incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a semiconductor device, and in further detail, it relates to a method for producing a semiconductor device comprising a gate electrode having a metallic silicide layer formed on the surface thereof.
2. Prior Art
In producing MOS transistors, gate electrodes and source/drain regions with low resistance have been implemented heretofore by employing a method comprising forming silicide films on the surface thereof (see, for instance, an unexamined published Japanese patent application Hei6 (1994)-132243).
In general, silicide is formed on the surface of the gate electrode and source/drain regions in accordance with the following procedure.
Referring first to FIG.
7
(
a
), a silicon oxide film and a polysilicon film are formed on an N well
33
formed on a silicon substrate
31
having an device isolation region
32
provided thereon, and after patterning the silicon oxide film and the polysilicon film as desired, a gate oxide film
34
and a gate electrode
35
are formed. A side wall spacer
36
is formed on the side wall of the gate electrode
35
thereafter.
Then, as shown in FIG.
7
(
b
), the surface of the silicon substrate
31
is subjected to ion implantation of boron difluoride
37
by using the gate electrode
35
and the side wall spacer
36
as masks. Then, the source/drain regions
38
are formed by applying thermal treatment thereto. By the ion implantation, boron difluoride
37
is implanted to the gate electrode
35
, at the same time, contaminants such as tungsten, etc., derived from members constituting the ion implantation apparatus, are incorporated into the gate electrode
35
and the source/drain regions
38
.
Referring to FIG.
7
(
c
), the contaminants
40
remaining on the upper surface of the gate electrode
35
and on the source/drain regions
38
that are not covered by the side wall spacer
36
are volatilized by heating with a lamp in an inert gas.
Then, the silicon of the gate electrode
35
and the source/drain regions
38
is exposed by removing the naturally oxidized film
39
on the surface of the gate electrode
35
and the source/drain regions
38
by using argon ion sputtering.
Subsequently, as shown in FIG.
7
(
d
), a titanium film
41
is vapor deposited on the entire surface of the silicon substrate
31
. Then referring to FIG.
7
(
e
), titanium is reacted with silicon by heating, and after removing the titanium film
41
remaining unreacted, a titanium silicide film
42
is formed on the surface of the gate electrode
35
and the source/drain regions
38
.
In the case where a MOS transistor is produced by forming the titanium silicide film
42
in accordance with the method above, however, the MOS transistor sometimes suffers an extremely low reliability ascribed to the deterioration of the gate oxide film
34
.
This is attributed to the fact that the contaminants such as tungsten, etc., that are incorporated during the ion implantation in forming the gate electrode and the source/drain regions induce an excessive reaction inside the gate electrode and the source/drain regions by the heat treatment for forming the silicide film.
More specifically, ion implantation is generally performed by using an ion implantation apparatus comprising an ion source comprised an arc chamber and a filament which are made of tungsten. Tungsten from the ion source generates divalent tungsten fluoride ions during the implantation of boron difluoride ions. These divalent ions undergo change in charge after passing through the draw out electrode to form trivalent ions before entering the magnet of mass analyzer. Thus are formed tungsten monofluoride ions (WF
+++
, having a mass number of 44.2 to 45.6), tungsten difluoride ions (WF
2
+++
, having a mass number of 48.4 to 49.9), etc. Hence, it is believed that, because these trivalent tungsten fluoride ions have a mass number near to 49, i.e., the mass number of boron difluoride, they cannot be completely removed at the slit of the mass analyzer, and are thereby implanted into the silicon substrate (see, for example, “Contamination in ULSI Production” (Tsuneo Ajioka et al., July 1999, pp. 304-311)).


REFERENCES:
patent: 5134301 (1992-07-01), Kamata et al.
patent: 5216253 (1993-06-01), Koike
patent: 5857889 (1999-01-01), Abbott
patent: 6239440 (2001-05-01), Abbott
patent: 6281556 (2001-08-01), Gerritsen et al.
patent: 0 964 426 (1999-12-01), None
patent: 6-132243 (1994-05-01), None
“Tungsten Contamination in BF2Implants”, Liebert et al., XP 10220578, Jun. 1996, pp. 135-138.
“Effect of BF2Induced Mo++on Long Retention Time in 0.25 &mgr;m DRAM Technology”, Curello et al., pp. 550-553.
“High Density Plasma Flood System for Wafer Charge Neutralisation”, Ito et al., pp. 478-481.

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