Solid state image sensor and method for fabricating the same

Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation

Reexamination Certificate

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Details

C438S073000, C438S060000, C438S075000

Reexamination Certificate

active

06187608

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid state image sensor, and more particularly, to a solid state image sensor and a method for fabricating the same having a wide light reception area.
2. Discussion of the Related Art
A conventional solid state image sensor will be explained with reference to FIGS.
1
and
2
A-
2
E.
FIG. 1
illustrates a layout of the conventional solid state image sensor, and
FIGS. 2A-2E
illustrate relevant sections of the conventional solid state image sensor shown in FIG.
1
.
The conventional solid state image sensor has a 4-phase clock applied thereto for transfer of image charges generated in a photoelectric conversion region
1
. As means for applying a clock signal, two layers including first and second transfer lines
2
and
3
, respectively, are insulated from each other by an insulating film
4
, between a plurality of the photoelectric conversion regions
1
. The underlying first transfer line
2
is insulated from a semiconductor substrates by another insulating film
6
.
Of the 4-phase clock signals applied to the transfer lines
2
and
3
, clock signals &phgr;
1
and &phgr;
3
are applied to the first transfer line
2
, and clock signals &phgr;
2
and &phgr;
4
are applied to the second transfer line
3
.
Each of the first and second transfer lines
2
and
3
includes transfer electrodes formed repeatedly in transfer line regions to correspond to the photoelectric conversion regions
1
. Upon repeated application of the &phgr;
1
, &phgr;
2
, &phgr;
3
and &phgr;
4
clock signals to the first and second transfer lines
2
and
3
having the aforementioned system, respectively, a potential in the underlying transfer line region is changed to transfer the image charges therein toward one direction.
However, in the formation of the first and second transfer lines for applying the 4-phase clock signals in the conventional solid state image sensor, and in view of its process, since the first transfer line should be formed wider than the second transfer line for forming the second transfer line on the previously formed first transfer line, a fill factor (or aperture ratio) is reduced and, consequently, a light sensitivity is decreased. The more the pixel is packed, the more the fill factor is reduced because the number of transfer lines increases as the number of pixels increases.
Therefore, the aforementioned conventional device structure does not allow a highly packed solid state image sensor.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a solid state image sensor and a method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a solid state image sensor and a method for fabricating the same for improving a light sensitivity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the solid state image sensor includes a semiconductor substrate, a plurality of photoelectric conversion regions formed under the surface of the substrate for generating image signals, and a plurality of charge transfer regions formed under the surface of the substrate responsive to clock signals applied through transfer lines for transferring the image signals in one direction, including at least one of a plurality of transfer lines formed of a transparent conductive material corresponding to one of the photoelectric conversion regions.
In another aspect, the present invention provides a solid state image sensor including a semiconductor substrate having a surface under which a matrix of photoelectric conversion regions and charge transfer regions are formed, each of the charge transfer regions being formed between adjacent photoelectric conversion regions arranged in a first direction; a first insulating film formed on the surface of the semiconductor substrate; a first transfer line insulated from the semiconductor substrate by the first insulating film, the first transfer line being arranged in a second direction transverse to the first direction between adjacent two photoelectric conversion regions; first transfer electrodes each formed connected to the first transfer line to correspond to one of the photoelectric conversion regions; second transfer electrodes each formed spaced from and opposite to the first transfer electrode on a charge transfer region in which the first transfer electrode is not formed; and, a second transfer line formed on the photoelectric conversion regions, the second transfer line being in contact with the second transfer electrodes formed in the second direction through contact holes in a second insulating film.
In another aspect of the present invention, a solid state image sensor comprises a semiconductor substrate; a plurality of transfer lines over the substrate and receiving clock signals, at least one of the plurality of transfer lines having a transparent conductive material; a plurality of transfer electrodes connected to the transfer lines; a plurality of photoelectric conversion regions under a surface of the substrate and generating image signals; and a plurality of charge transfer regions under the surface of the substrate transferring the image signals from the photoelectric conversion regions in response to the clock signals from the transfer lines.
In another aspect of the present invention, a solid state image sensor comprises a semiconductor substrate having a surface; a matrix of photoelectric conversion regions and charge transfer regions under the surface of the semiconductor substrate, each of the charge transfer regions located between adjacent photoelectric conversion regions arranged in a first direction; a first insulating film on the surface of the semiconductor substrate; a first transfer line insulated from the semiconductor substrate by the first insulating film, the first transfer line being arranged in a second direction transverse to the first direction between adjacent two photoelectric conversion regions; first transfer electrodes each connected to the first transfer line corresponding to one of the photoelectric conversion regions; second transfer electrodes each spaced from and opposite the first transfer electrode on a portion of the charge transfer region; a second insulating film having contact holes on the second transfer electrodes; and a second transfer line on the photoelectric conversion regions, the second transfer line being in contact with the second transfer electrodes in the second direction through the contact holes.
In another aspect of the present invention, a solid state image sensor comprises a semiconductor substrate having a surface; a matrix of photoelectric conversion regions and charge transfer regions under the surface of the semiconductor substrate, each of the charge transfer regions located between adjacent photoelectric conversion regions arranged in a first direction; a first insulating film on the surface of the semiconductor substrate; first and second transfer electrodes spaced from each other and insulated from the semiconductor substrate by the first insulating film, each of the first and second transfer electrodes being arranged in a second direction transverse to the first direction corresponding to the photoelectric conversion regions; a second insulating film on first and second transfer electrodes; and first and second transfer lines at first and second sides on the photoelectric conversion regions in contact with the first and second transfer electrodes, respectively

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