Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2000-11-07
2003-08-12
Fahmy, Wael (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C250S206000, C250S370010, C257S225000
Reexamination Certificate
active
06605850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid-state image pickup device having a photoelectric conversion element for converting light into an electrical signal and a method of manufacturing the same.
2. Related Background Art
In recent years, as solid-state image pickup devices have smaller size, higher density, and higher resolution, a decrease in light-receiving sensitivity due to a decrease in aperture area of a region which is not covered by a light-shielding portion on the light incoming side of a photoelectric conversion element or a decrease in light-receiving area of the photoelectric conversion element poses a problem. To improve sensitivity, a lens that condenses incoming light is provided above the photoelectric conversion element to increase the aperture area of the solid-state image pickup device in effect.
A prior art of a solid-state image pickup device with such microlens will be explained below with reference to
FIG. 1
in relation to Japanese Patent No. 2,558,389. Referring to
FIG. 1
, a photoelectric conversion element
102
is formed on a semiconductor substrate
101
, and an insulating layer
103
is formed on the photoelectric conversion element
102
and the remaining surface of the semiconductor substrate
101
. A polysilicon transfer electrode portion
104
for transferring photocharges of the photoelectric conversion element
102
is formed on the insulating layer
103
on the remaining surface of the semiconductor substrate
101
, and an aluminum light-shielding portion
105
is formed on top of it. A surface passivation layer
106
is formed on the light-shielding portion
105
, and a leveling layer
107
that consists of a transparent polymer resin and levels the element surface is formed thereon. Furthermore, a concave microlens layer
108
composed of a transparent polymer resin or materials such as casein, gelatin, and the like is formed, and an inter-lens layer
109
consisting of a transparent polymer resin is formed thereon. A round, convex microlens layer
110
consisting of a transparent polymer resin or casein, gelatin, and the like is formed on the interlayer
109
, and a passivation layer
111
consisting of a transparent polymer resin is formed thereon.
With this structure, since the convex microlens layer
110
condenses light, sensitivity can be improved. Also, since the inter-lens layer
109
is interposed between the convex and concave microlens layers
110
and
108
, the refraction index of the convex microlens layer
110
and its surface curvature required for focusing light to a size equivalent to that of an aperture portion on the concave microlens layer
108
can be reduced.
Let na, nb, nc, and nd be the refraction indices of the convex microlens layer
110
, inter-lens layer
109
, concave microlens layer
108
, and leveling layer
107
, respectively. If na>nb, nc>nb, and nc>nd, i.e., (na, nc)>(nb, nd), light can be condensed most efficiently and can enter the photoelectric conversion element nearly perpendicularly, thereby suppressing production of smear noise, and achieving a high S/N ratio.
Furthermore, since the leveling layer
107
sends light onto the surface of the photoelectric conversion element nearly perpendicularly and therefore the refraction index of the concave microlens and its surface curvature can be reduced, the device can be easily manufactured.
However, a microlens is used to assure an effective aperture ratio despite a small pixel size of the solid-state image pickup device of a photosensor, and the aperture ratio is improved by combining convex and concave lenses. This complicates the layer structure, resulting in high manufacturing cost and low manufacturing yield. Also, a plurality of alignment processes are required, and the effective aperture ratio cannot be desirably improved.
As a recent device has higher density, higher resolution, and smaller size, it is hard to match the optical axis of the microlens placed above the photoelectric conversion element as an underlayering device with the condensed point.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a solid-state image pickup device which is suitable for higher density, higher resolution, or smaller size, and a method of manufacturing the same.
In order to achieve the above object, according to an aspect of the present invention, there is provided a solid-state image pickup device comprising: a plurality of photoelectric conversion elements formed in a semiconductor substrate; conductive layers formed on the semiconductor substrate between the neighboring photoelectric conversion elements via an interlayer layer; a first interlayer layer formed on the photoelectric conversion elements and conductive layers; a second interlayer layer formed on the first interlayer layer; and microlenses formed above the photoelectric conversion elements, wherein a refraction index of the first interlayer layer located above the photoelectric conversion elements is different from a refraction index of the second interlayer layer.
According to another aspect of the present invention, there is provided a method of manufacturing a solid-state image pickup device, comprising the steps of: forming a plurality of photoelectric conversion elements in a semiconductor substrate; forming light-shielding layers or signal wire for outputting signals from the photoelectric conversion elements on the semiconductor substrate between the neighboring photoelectric conversion elements via an interlayer layer; forming a first interlayer layer on the photoelectric conversion elements and the light-shielding layer or signal wire; forming a second interlayer layer on the first interlayer layer; and forming microlenses above the photoelectric conversion elements, wherein the microlenses forming step including steps of forming the first interlayer layer by CVD, forming the second interlayer layer having a refraction index different from a refraction index of the first interlayer layer on a surface of the first interlayer layer by CVD, leveling a surface of the second interlayer layer by polishing by CMP, coating a microlens material resin onto the leveled surface, softening the material by heating, and hardening the material.
Furthermore, according to the present invention, there is provided a solid-state image pickup device comprising: a plurality of photoelectric conversion elements formed in a semiconductor substrate; an interlayer layer formed above the photoelectric conversion elements; and light-shielding means for shielding light, wherein the interlayer layer is formed with a step using a step of the light-shielding means.
According to still another aspect of the present invention, there is provided a method of manufacturing a solid-state image pickup device, comprising the steps of: forming a plurality of photoelectric conversion elements in a semiconductor substrate; forming an interlayer layer above the photoelectric conversion elements; and forming light-shielding means on a flat surface above the photoelectric conversion elements, wherein the interlayer layer is formed on a surface including at least the light-shielding means.
Other objects and features of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.
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Hiyama Hiroki
Kochi Tetsunobu
Koizumi Toru
Ogawa Katsuhisa
Sakurai Katsuhito
Fahmy Wael
Pizarro-Crespo Marcos D.
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