Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1998-12-03
2004-04-13
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S275000, C348S315000, C250S208100, C257S223000, C257S229000
Reexamination Certificate
active
06721005
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state image sensor, in particular, it relates to a solid-state image sensor being provided with an effective pixel area which performs photoelectric conversion in taking in rays of light and an optical black area which forms a reference black level.
Examples of a solid-state image sensor includes a CCD (Charge Coupled Device) image sensor, a CMOS image sensor, etc. A CCD image sensor
1
as shown in
FIG. 3
is provided with an effective pixel area
2
having a light receiving portion which performs photoelectric conversion by taking in light and an optical black area
3
which forms a reference black level without taking in light.
In the effective pixel area
2
, a plurality of effective pixels (not shown in a drawing), each having a light receiving portion, are disposed in vertical and horizontal directions, similarly, in the optical black area
3
, a plurality of optical black pixels are disposed in vertical and horizontal directions.
An effective pixel in the effective pixel area
2
is composed of a light receiving portion
11
which performs photoelectric conversion and is formed on the surface layer portion of a silicon substrate
10
as shown in
FIG. 5A. A
transfer register
13
is formed on one side of the light receiving portion
11
through a read gate
12
and a channel stop
14
is formed on the other side of it. A transfer electrode
16
is formed on the silicon substrate
10
covering a part right above the transfer register
13
through an insulating film
15
and has an opening port in a part right above the light receiving portion
11
. The opening port part of the transfer electrode
16
forms an electrode opening port portion
16
a
having a rectangular shape as shown in FIG.
6
.
Further an inter-layer insulating film
17
is formed covering the transfer electrode
16
and a light shielding film
18
made of aluminum (Al) is formed over the inter-layer film
17
on the silicon substrate
10
as shown in FIG.
5
A. The light shielding film
18
is provided with an opening port
19
which opens right above part of the light receiving portion
11
, that is, in in communication with the electrode opening port
16
a.
Light is led in through the opening port
19
and the light is input onto the light receiving portion
11
. And other light is shielded from coming in.
On the other hand, the optical black pixels in the optical black area
3
have almost the same constitution as that of the effective pixels in the effective pixel area
2
. However, they are different from the effective pixels only in that they do not have opening ports
19
in the light shielding film
18
as shown in
FIG. 5B
(Refer to FIG.
6
.). Otherwise, the effective pixels and the optical black pixels have the same construction including the electrode opening port portion
16
a
not being covered with the transfer electrode
16
and also the transfer register
13
, the channel stop
14
, etc. being incidental to the transfer electrode
16
, which means that the effective pixels and the optical black pixels have the same unit cell size.
The reason why the electrode opening port
16
a
is also made in the optical black area
3
is that in the total pixel area
4
(
FIG. 3
) composed of the effective pixel area
2
and the optical black area
3
, before the patterning is performed to form the opening port
19
on the shielding film
18
, the effective pixel area
2
and the optical black area
3
are not separately processed and they are processed in the same way in order to simplify the manufacturing process. As described in the above, before the patterning of the light shielding film
18
is performed, the effective pixel area
2
and the optical area
3
are processed in the same way. So that when the patterning for forming the transfer electrode
16
, is performed the same sized electrode opening port portions
16
a
are formed in both the effective pixel area
2
and the optical black area
3
.
In recent years, solid-state image sensors such as CCD image sensors have been improved in order to respond to the demand for higher sensitivity, higher degree of integration and further miniaturization. However, nowadays, the requests for the miniaturization, etc. exceeds the speed of improvement, and further new improvements are demanded.
In the past, as a technique to respond to the demand for improving the degree of integration, the technique of making the light shielding film thinner was proposed, and is used in a part of actual production. However, it can be considered that the thickness of the film may become so thin that transmission of light sometimes occurs because of the dispersion in manufacturing. In such a case, since the electrode opening port portion
16
a
and the light receiving portion
11
are also formed in the optical black area
3
in the same way as in the case of the effective pixel area
2
, photoelectric conversion may occur in the light receiving portion
11
in the optical black area
3
, which may alter the reference black level and cause a malfunction.
SUMMARY OF THE INVENTION
The present invention was invented in consideration of the above-mentioned circumstances, and the object of the present invention is to offer a solid-state image sensor in which higher sensitivity, higher degree of integration and further miniaturization are possible and also the reference black level can be kept in a stable state.
A solid-state image sensor according to the present invention includes an effective pixel area having a light receiving portion which performs photoelectric conversion by taking in light and an optical black area which provides a reference black level without taking in light. The light receiving portion is formed in an electrode opening port portion which is not covered by a transfer electrode. An electrode opening port portion which is not covered by the transfer electrode in the optical black area is formed smaller than that in the effective pixel area as a means to solve the above-mentioned problem.
In the case of a solid-state image sensor of this type, because the electrode opening port portion formed in the optical black area is made smaller than that in the effective pixel area, a unit cell size of the optical black pixels is made smaller than the unit cell size of the effective pixels. Therefore, when the solid-state image sensor of this type is manufactured, theoretical yield of chips obtained from a wafer is increased and the optical black area is narrowed down because of the smaller size of a unit cell. Thus the effective pixel area can be increased corresponding to the narrowed down area in the optical black area, which makes it possible to upgrade the sensitivity and the degree of integration.
Further, since the electrode opening port portion of the optical black area is formed narrow, even when the transmission of light occurs with the tendency of thinning the light shielding film, the quantity of incoming light is small. Therefore, it is possible to control the quantity of photoelectric conversion in the optical black area to be sufficiently.
A solid-state image sensor according to the present invention may also be provided with an effective pixel area having a light receiving portion which performs photoelectric conversion by taking in light and an optical black area which forms a reference black level without taking in light, in which the light receiving portion is formed inside the electrode opening port portion which is not covered with a transfer electrode and an electrode opening port portion which is not covered with the transfer electrode is not formed in the optical black area. This will be a means for solving the above-mentioned problem.
In the case of a solid-state image sensor of this type, because an electrode opening port portion is not formed in the optical black area, a unit cell size of an optical black pixel becomes smaller than that of an effective pixel. Therefore, for example, when a solid-state image sensor of this type is manufactured, the theoretical yield o
Garber Wendy R.
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
Villecco John M.
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