Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-03-26
2001-07-03
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S216000, C257S432000, C438S070000
Reexamination Certificate
active
06255640
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid-state image sensing device and a method for manufacturing a solid-state image sensing device.
2. Description of the Related Art
In recent years, a solid-state image sensing device has been miniaturized and its pixel becomes increasingly densified, with which a light receiving area is reduced and a deterioration of characteristics such as a drop of the sensitivity or the like is caused.
It has been proposed as measures against the drop of sensitivity to promote a light collecting efficiency on to a light receiving sensor unit by providing, e.g. a microlens, that is called an on-chip lens and an intra-layer lens.
A structure of the conventional solid-state image sensing device will be described below.
FIG. 1
shows a schematic sectional view of a conventional solid-state image sensing device
100
in the solid-state image sensing device with a structure having an intra-layer lens.
As shown in
FIG. 1
, a large number of light receiving sensor units
102
for performing the photoelectric conversion are formed in an array on a silicon substrate
101
.
On one side of the light receiving sensor unit
102
is formed a charge transfer element
104
through a readout gate
103
. On the other side thereof is formed a charge transfer element
104
to the other light receiving sensor unit
102
through a channel stop
105
.
A signal charge derived from the photoelectric conversion by the light receiving sensor unit
102
is read out to the one charge transfer element
104
through the readout gate
103
and further transferred by the charge transfer element
104
.
Moreover, on the surface of the silicon substrate
101
is provided a SiO
2
insulator film
106
formed by the thermal oxidation method or CVD (Chemical Vapor Deposition) method, and so forth.
On the insulator film
106
nearly just above the charge transfer element
104
is formed a transfer electrode
107
made of polysilicon, and besides another transfer electrode (not shown) is formed in such a manner as partially overlapped with the transfer electrode
107
.
On the surface of these transfer electrodes
107
, i.e. on the top surface and the side surface thereof is formed, an interlayer insulator film
108
which covers the transfer electrode
107
and further covers the insulator film
106
on the light receiving sensor unit
102
facing between the transfer electrodes
107
.
On the interlayer insulator film
108
is formed a light shielding film
109
which covers the transfer electrode
107
. The light shielding film
109
has an overhang portion
109
a
which projects just over the light receiving sensor unit
102
in order to restrict a smear. An opening
110
is formed just over the light receiving sensor unit
102
in such a manner as surrounded by the overhang portion
109
a
. In addition, the light shielding film
109
is formed by a metal of high melting point, e.g. tungsten.
On the light shielding film
109
is formed an interlayer film
111
made of BPSG (boron phosphorus silicate glass), which covers the light shielding film
109
and the interlayer insulator film
108
facing the opening
110
. The interlayer film
111
is subjected to the reflow processing in order to form a recess
111
a
formed on the light receiving sensor unit
102
between the transfer electrodes
107
. This recess
111
a
is processed to be adjusted to have a required curvature.
On this interlayer film
111
is formed a passivation film
112
covering its surface.
The recess
111
a
of the interlayer film
111
is filled by an intra-layer lens material which forms an intra-layer lens
114
over the passivation film
112
, the lens having a protuberance with the required curvature in accordance with the recess
111
a.
This intra-layer lens
114
is made flat of its surface by the known so-called resist etch back process or the CMP process (chemo-mechanical polishing process).
On the flattened intra-layer lens
114
is formed a color filter layer
116
. This color filter layer
116
can be formed by a known process using such resin, and so forth. into which a pigment is dispersed.
On the color filter layer
116
is formed a microlens
117
made of a transparent resin and the like. The microlens
117
directs an incident light to the opening
109
a
of the light shielding film
109
through the intra-layer lens
114
so that the light may be incident onto the light receiving sensor unit
102
. Therefore, the curvature of the microlens
117
is chosen to have a desired value depending on a distance from the light receiving sensor unit
102
to the bottom plane of the microlens
117
in the solid-state image sensing device
100
shown in FIG.
1
.
However, the solid-state image sensing device with the arrangement shown in
FIG. 1
causes the following inconvenience.
Specifically, because the solid-state image sensing device
100
having the structure including the intra-layer lens
114
shown in
FIG. 1
is provided with the intra-layer lens
114
and the color filter layer
116
respectively, an overall thickness from the light receiving sensor unit
102
to the bottom plane of the microlens
117
reaches the extent of 4 to 5 &mgr;m or more. This means that there is a large distance between the light receiving sensor unit
102
and the microlens
117
.
When the distance from the light receiving sensor unit
102
to the microlens
117
becomes large in this manner, in the case where an incident light inclined relative to the microlens
117
increases, if the diaphragm of an image sensing lens of camera is opened as shown in
FIG. 2
, the light collected by the microlens
117
will deviate from the center of the opening of the light shielding film
109
as shown by broken lines in
FIG. 2
, thereby causing a rate of collecting the light onto the light receiving sensor unit
102
to be lowered. In other words, the dependence on F value goes worse and so the sensitivity to the parallel light is satisfactory, whereas the sensitivity drops remarkably toward the diaphragm being opened. Moreover, when the collected light approaches an opening end of the light shielding film
109
, a signal charge is caused to be mixed in the adjacent light receiving sensor unit
102
or charge transfer area (not shown), thus making what is called a smear to occur.
Furthermore, because the curvature of the microlens
117
is determined depending on the distance from the light receiving sensor unit
102
to the microlens
117
as described above, when the distance from the light receiving sensor unit
102
to the microlens
117
increases, it will be necessary to make larger the curvature of the microlens accordingly.
When the curvature of the microlens
117
on the color filter
116
becomes large in this manner, a light L collected by the microlens
117
is rejected by an edge of the color filter
116
, as shown in FIG.
1
. This effects an increase of minute black spots, this causing the deterioration of picture quality.
SUMMARY OF THE INVENTION
In view of the above circumstances, it is an object of the invention to provide a solid-state image sensing device having a structure in which the distance from the light receiving sensor unit
102
to the microlens
117
is made shorter in order to eliminate the aforesaid inconvenience.
According to an aspect of the present invention, there is provided a solid-state image sensing device which comprises a light receiving sensor unit for making the photoelectric conversion on a substrate, an interlayer film having a recess above the light receiving sensor unit, and an intra-layer color filter, on the interlayer film, having a protuberance formed by filling the recess and following the curved surface of the recess, the protuberance having a curvature required for collecting the incident light onto the light receiving sensor unit. The intra-layer color filter has both functions of the intra-layer lens for collecting the incident light onto the light receiving sensor unit as well as the color filter, thus playing both these two role
Endo Hiroki
Natori Taichi
Kananen Ronald P.
Lee John R.
Rader Fishman & Grauer
Sony Corporation
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