Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2000-04-07
2003-10-07
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S432000
Reexamination Certificate
active
06630722
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a solid state image sensing device and a fabricating method of the device, and, in particular, to a solid state image sensing device in which a color filter is formed on a photoelectric conversion section (light-receiving section) and a fabricating method of the device.
There has conventionally been a CCD solid state image sensing device whose unit cell is shown in a cross-section view of FIG.
2
. The groundwork device of this CCD solid state image sensing device has a periodical gap in level of several micrometers due to the provision of electrodes
3
and light-shielding films
5
. The uppermost surface of the groundwork device is covered with a protecting film
6
made of Si
3
N
4
or the like. Therefore, in the so-called on-chip process to be performed subsequent to the formation of the groundwork device, it is required to reduce the difference in level of the groundwork device by forming a flattening layer
7
by spin coating a transparent flattening material prior to the formation of color filters
8
,
9
and
10
and thereafter form the color filters
8
,
9
and
10
.
However, in accordance with the progress of the improvement in integration density of pixels, there is a growing demand for the contraction of the device in the z-direction in addition to the contraction in the x- and y-directions. In
FIG. 2
are shown a substrate
1
, a light-receiving section (photoelectric conversion section)
2
, an interlayer insulating film
4
, a protecting layer
11
and a microlens
12
.
FIG. 3
shows a schematic view of an optical system in the unit cell shown in FIG.
2
. In
FIG. 3
, if a distance L in the z-direction from the light-receiving section
2
to the microlens
12
is long, then an oblique incident light
15
is shielded by a projecting portion
13
constructed of the electrode
3
and the like. Therefore, the incident light cannot be effectively utilized. It is to be noted that the reference numeral
14
denotes a perpendicular incident light.
In an image-taking device (camera or the like) employing a solid state image sensing device, its optical system has become compacted together with the development in integration density, and accordingly, there is a growing trend toward employing a lens having a very short exit pupil position. As shown in
FIG. 4
, the lens having a very short exit pupil position is characterized in that the rate of the oblique incident light
20
relative to the total luminous flux incident on an imaging region
17
of the solid state image sensing device
16
is increased since the incident angle of light on the surface of the solid state image sensing device
16
becomes increased in comparison with the normal lens in the case of the short exit pupil position lens
18
. As a result, the quantity of incident light looses its uniformity between the center portion and the peripheral portion of the imaging region
17
, consequently generating a shading phenomenon. This shading phenomenon occurs principally because the luminous flux tends to be scattered by the projecting portions (including the light shielding film) constructed of the transfer section of the solid state image sensing device
16
since the incident angle of the oblique incident light
20
is greater in the peripheral portion than in the center portion of the imaging region
17
. Then, this shading phenomenon occurs more significantly as the distance in the z-direction from the light-receiving section of the solid state image sensing device
16
to the microlens increases, as described above. It is to be noted that the reference numeral
19
denotes a perpendicular incident light.
On the other hand, there is a demand for improving the image quality in terms of the tone of color, and it is required to further improve the quality of the transmission color spectral characteristic of the color filter in accordance with the requirement. It is, then, required to improve the quality of hue for the above purpose, and increasing the film thickness of the color filter can cope with this. However, increasing the film thickness of the color filter is not compatible with the requirement of the aforementioned contraction in the z-direction.
There is another severe requirement for the registration (alignment accuracy) with respect to the aforementioned groundwork device in the process of forming the color filters
8
,
9
and
10
and the microlens
12
in
FIG. 2
in forming a solid state image sensing device, due to the high integration as described above, in comparison with the conventional requirement. In this case, with regard to the wafer alignment, the groundwork device and the upper layer are aligned in position with each other by detecting light obtained by reflecting and refracting a beam of laser light from the alignment mark formed on the groundwork device via the flattening layer
7
. However, the focus position detection of the alignment mark via the flattening layer
7
having a thickness of several micrometers tends to optically cause a large detection error.
Such a detection error sensitively exerts bad influence on the image quality when applied to the case where the color filters
8
,
9
and
10
are formed on the flattening layer
7
. That is, as shown in
FIG. 5
, a cross-talk light (mixture color light)
22
incident on the adjacent pixel
21
′ increases in ratio to the normal light
23
as the thickness H of the flattening layer
7
increases even if the quantity of displacement D between the pixel
21
and the color filters
8
,
9
and
10
is identical.
The above has described several problems, which have emerged as the problems in accordance with the development in the integration density of the solid state image sensing device. These problems are attributed to the formation of the color filters
8
,
9
and
10
after the formation of the thick flattening layer
7
(in other words, with a long distance between ground work device surface and color filters provided in the z-direction) on the groundwork device.
As a method for resolving the aforementioned problems, there is a known solid state image sensing device color filter fabricating method as disclosed in the prior art reference of Japanese Patent Laid-Open Publication No. HEI 3-98002. This solid state image sensing device color filter fabricating method will be described below with reference to FIG.
6
.
First, as shown in
FIG. 6A
, a stepped portion
27
constructed of an electrode, a light shielding film or the like is formed between light-receiving sections (photoelectric conversion sections)
26
on a substrate
25
, by which a solid state image sensing device is obtained. Then, a resist layer
28
is coated on this solid state image sensing device, filling the portions having a difference in level between the stepped portions
27
with the layer. Next, as shown in
FIG. 6B
, a plurality of specified regions around the light-receiving sections
26
of an identical color are opened through the resist layer
28
, and a polymer resin layer (referred to as a coloring layer hereinafter)
29
that includes dye of the corresponding color is formed throughout the entire surface including the opening portions
31
, consequently burying the coloring layer
29
in the aforementioned specified regions. Next, as shown in
FIG. 6C
, the coloring layer
29
is etched back to leave the coloring layer
29
only in the opening portions. Subsequently, as shown in
FIG. 6D
, the resist layer
28
is removed by a releasing liquid.
Then, by repeating a series of processes shown in
FIGS. 6A through 6D
for the light-receiving sections
26
of all the colors and laying a plurality of coloring layers
29
a
through
29
d
on all the light-receiving sections
26
, the coloring layers
29
a
through
29
d
are formed into color filters. Subsequently, a flattening layer
30
is formed.
However, the solid state image sensing device color filter fabricating method disclosed in the prior art reference of Japanese Patent Laid-Open Publication No. HEI 3-98002 has the f
Gebremariam Samuel A
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
Thomas Tom
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