Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
1998-02-04
2001-02-13
Loke, Steven H. (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S413000, C257S751000, C257S755000, C257S758000
Reexamination Certificate
active
06188119
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and its method of manufacture, and in particular, relates to a semiconductor device in which there is contact between a polysilicon electrode and metal electrode in a gate region, and a manufacturing method for such a semiconductor device.
2. Description of the Related Art
FIG. 1
is a plan view of a MOS transistor of the prior art. The prior-art MOS transistor is formed from gate electrode
97
composed of polysilicon, drain region
94
, and source region
95
. Gate electrode
97
, drain region
94
and source region
95
are each connected to metal wiring
91
by means of contacts
99
. Contacts
99
are formed on element isolation region
93
formed from a thick silicon oxide film that covers the field region. However, gate electrode
97
of the transistor is fabricated at close to the limits of accuracy of methods such as lithographic processing, and the formation of contacts
99
in the gate region is therefore difficult. Contacts
99
are therefore provided on the element isolation region
93
apart from the gate region.
However, in a semiconductor device in which an electrode formed from polysilicon is provided over a wide area, such as in a CCD (Charge Coupled Device) solid-state image-sensing device, a polysilicon electrode has a sheet resistance on the order of 20~50 &OHgr;/□. This sheet resistance can be reduced by providing a metal electrode on the rear surface of the polysilicon electrode and by providing contacts for connection with the metal electrode directly over the polysilicon electrode.
FIG. 2
is a schematic sectional view of this type of prior-art solid-state image-sensing device. In this prior-art solid-state image-sensing device, charge transfer electrodes
108
and
110
are provided on diffusion region
100
. Change to lower sheet resistance is then brought about by first connecting polysilicon wiring
101
with charge transfer electrode
108
or
110
by way of contact
101
a
, and connecting aluminum layer
103
with this polysilicon wiring
101
by way of contact
103
a.
Here, a method of connecting aluminum layer
103
with charge transfer electrode
108
or
110
by means of contact
103
a
has also been considered, but such a method could not be employed because aluminum layer
103
tends to diffuse within polysilicon electrode and therefore deposits on the gate insulation film surface partially, thereby resulting in such problems as alteration of the silicon surface potential and lowering of the dielectric strength of the oxide film.
FIG. 3
is a schematic sectional view showing a prior-art solid-state image-sensing device for solving the above-described problems.
This solid-state image-sensing device of the prior art is described at pages 105~108 of the preliminary papers of the 1992 IEDM (International Electronic Devices Meeting).
This solid-state image-sensing device of the prior art employs tungsten layer
105
in a shield layer, this tungsten layer
105
being connected with charge transfer electrode
108
and charge transfer electrode
110
by way of contacts
105
a
. Tungsten layer
105
simultaneously serves as a shield layer and wiring.
Tungsten is not as prone as aluminum to diffuse into a polysilicon electrode, and as a result, when tungsten layer
105
is used as wiring, it can directly connect with charge transfer electrodes
108
and
110
by way of contact
105
a.
This solid-state image-sensing device of the prior art enables a greater reduction of the sheet resistance than the solid-state image-sensing device of
FIG. 2
by using tungsten layer
105
for wiring in place of an aluminum layer. This element also provides the effect of greatly reducing the series parasitic resistance of the power source of charge transfer electrodes
108
and
110
. The preliminary papers of the IEDM mentioned hereinabove also include a description of a CCD image sensor that applies the solid-state image-sensing device of FIG.
3
.
In the above-described semiconductor devices of the prior art, however, a conductive film of, for example, tungsten comes in direct contact with a silicon electrode composed of polysilicon or single-crystal silicon, and CCD solid-state image-sensing devices of this construction therefore entail problems such as the occurrence of changes in threshold value or channel potential as well as drops in the charge transfer efficiency.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a semiconductor device that operates stably without changes in channel potential or threshold value voltage despite direct contact between a conductive film constituted by a metal film and a silicon electrode.
To achieve the above-described object, the semiconductor device of the present invention includes:
first insulation film formed on the semiconductor substrate;
a silicon electrode that is formed on the first insulation film and that is made up of polysilicon or single-crystal silicon;
a second insulation film that is formed to cover the silicon electrode and that has an opening over the silicon electrode;
a barrier metal layer that is formed on the surface of the silicon electrode exposed in the opening and that is made up of a metal silicide; and
a conductive film formed on the opening and on the second insulation film.
The present invention is a device provided with a barrier metal layer made up of a metal silicide between a silicon electrode and a conductive film.
As a result of this construction, a semiconductor device can be obtained that has a stable characteristic wherein channel potential or threshold value voltage does not change despite contact with the conductive film over the silicon electrode.
In addition, the semiconductor device of the present invention may include a titanium nitride film and titanium film between the second insulation film and the conductive film.
As a result, not only can the contact between the conductive film and second insulation film be improved; but the titanium nitride film and titanium film can be used as an etching barrier when patterning the conductive film; damage to the second insulation film, which is the ground when etching, can be reduced; and micro-patterning of the conductive film can be easily accomplished.
In addition, the semiconductor device of the present invention may include a titanium film formed between the second insulation film and the conductive film.
As a result, not only can the contact between the conductive film and the second insulation film be improved; but the titanium film can be used as an etching barrier when patterning the conductive film; damage to the second insulation film, which is the ground when etching, can be reduced; and micro-patterning of the conductive film can be easily accomplished.
In addition, the semiconductor device of the present invention may include a barrier metal layer formed on the surface of the silicon layer formed on the silicon electrode.
As a result, the silicon electrode can be made a thin-film because there is no need to reserve space on the silicon electrode for forming a barrier metal layer, thereby enabling an improvement in evenness, an improvement in coverage of the conductive film, and a decrease in the occurrence of defects caused by etching residue.
According to an embodiment of this invention, the silicon layer or the barrier metal layer can be formed in a hemispherical form on the second insulation film.
As a result, a surface of superior evenness is obtained, whereby excellent coverage and patterning can be obtained when forming the conductive film, and in addition, because the thickness of the silicon layer can be freely set even in cases in which the second insulation film is thin, positions at the edges of the conductive film can be lowered, leakage of light to the charge transfer region can be reduced in cases of application to a solid-state image-sensing device, and smear can be decreased.
The semiconductor device of the present invention may also include a barrier metal layer that is
Hokari Yasuaki
Ogawa Chihiro
Loke Steven H.
NEC Corporation
Young & Thompson
LandOfFree
Semiconductor device having barrier metal layer between a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device having barrier metal layer between a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device having barrier metal layer between a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559649