Process for fabricating metal silicide layer by using ion...

Details Process for fabricating metal silicide layer by using ion... Process for fabricating metal silicide layer by using ion...

2000-10-12

2001-08-28

Lebentritt, Michael (Department: 2824)

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

C438S627000, C438S656000, C438S734000

Reexamination Certificate

active

06281087

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for fabricating a metal silicide layer by using ion metal plasma deposition, and more particularly to a process for fabricating a metal silicide layer which alleviates the bridging effect.
2. Description of the Prior Art
The continued miniaturization of integrated circuits has brought about an increasing need to reduce the sheet resistance in the source/drain and gate regions. In metal-oxide-semiconductor (MOS) device manufacturing, self-aligned metal silicide layers (also known as “salicide” layers) have been used in reducing the sheet resistance of the source/drain and gate regions.
FIGS. 1A-1F
show cross-sectional views illustrating the process flow of fabricating the metal salicide according to a conventional process. Referring to
FIG. 1A
, an oxide layer
11
a
and a polysilicon layer
12
a
are successively formed on a semiconductor substrate
10
. Then, referring to
FIG. 1B
, the oxide layer
11
a
and the polysilicon layer
12
a
are patterned by photolithography and etching to form a gate region
13
including the patterned oxide layer
11
and the patterned polysilicon layer
12
. Then, lightly-doped source and drain regions
22
are formed using a conventional ion implant method
20
using the gate region
13
as a doping mask.
Subsequently, referring to
FIG. 1C
, a dielectric layer is formed over the gate region
13
and the source/drain regions
22
, and then anisotropically etched using reactive ion etching (RIE) to form a spacer
14
on the sidewall of the gate region
13
.
Subsequently, referring to
FIG. 1D
, a heavily-doped source and drain regions
32
are formed using a conventional ion implant method
30
using the gate region
13
and the spacer
14
as a doping mask. Thus, source/drain regions
40
with a lightly doped drain (LDD) structure
22
is thus formed.
Subsequently, referring to
FIG. 1E
, a metal layer
50
is formed over the structure depicted in FIG.
1
D. Referring then to
FIG. 1F
, a rapid thermal process (RTP) is then performed to make the metal layer
50
react with the silicon of the polysilicon layer
12
and the source/drain regions
40
to form a metal silicide layer
52
on both the polysilicon layer
12
and the source/drain regions
40
, leaving the metal layer on the spacer substantially intact. Thus, a self-aligned metal silicide layer (also known as “salicide” layer) is formed. The metal layer
50
which did not react with silicon completely is then removed by wet etching.
One purpose of the spacer
14
is to separate the polysilicon layer
12
and the source/drain regions
40
. However, in the above method, some silicon particles of the substrate
10
are very likely to diffuse onto the spacer
14
during the rapid thermal process, which react with the metal and form unwanted metal silicide on the spacer
14
. This unwanted metal silicide can cause the polysilicon layer
12
to be undesirable short circuited to the source/drain regions
40
. This conditions is referred to as “bridging effect”.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process for fabricating a metal silicide layer, which alleviate a bridging effect.
To achieve the above object, the process for fabricating a metal silicide layer of the present invention includes:
providing a silicon substrate having a polysilicon gate region and source/drain regions thereon;
forming a spacer on a sidewall of the gate region;
forming a metal layer on the gate region and the source/drain regions by using ion metal plasma (IMP) deposition with substantially no metal layer formed on the spacer; and
transforming the metal layer into a metal silicide layer.


REFERENCES:
patent: 5882399 (1999-03-01), Ngan et al.
patent: 5966607 (1999-10-01), Chee et al.
patent: 5985759 (1999-11-01), Kim et al.
patent: 6025274 (2000-02-01), Lin et al.

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