Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
1999-09-29
2002-02-05
Meier, Stephen D. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S443000, C257S432000, C257S435000, C257S222000, C257S213000, C257S233000, C257S231000, C257S446000
Reexamination Certificate
active
06344666
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an amplifier-type solid-state image sensor device for obtaining a signal charge using a photoconverter such as a photodiode, amplifying and extracting the obtained signal charge, and more particularly relates to an amplifier-type solid-state image sensor device wherein the positional relationship between the photoconverter and an opening in a metal film which defines the region where light is received in the photoconverter, is improved.
A solid-state image sensor device for obtaining an image of an object using a lens has a problem that pixels near the center of the semiconductor chip have a different amount of light injected thereto from pixels near the peripheral portion of the semiconductor chip. More specifically, the amount of light in the center of the semiconductor chip is great, but the amount of light at the peripheral portion of the semiconductor chip is small. Consequently, the level of photo-sensitivity differs between at the center of the semiconductor chip and the peripheral portion of the semiconductor chip. Conventionally, this problem is solved by a method known as scaling, whereby the position of a microlens in the color filter portion is slightly displaced horizontally toward the center of the photodiode (by approximately 0.001 &mgr;m per pixel). Scaling prevents the level of photosensitivity at the peripheral portion of the semiconductor chip from falling below that at the center the semiconductor chip.
In a CCD-type solid-state image sensor device, as shown in
FIG. 6
, an aluminum lightproof film (or aluminum wire)
65
, which defines the opening in the photodiode
62
, covers capacitor electrodes (polysilicon) or gate wires (polysilicon)
63
and extends to the edge of the photodiode
62
. Therefore, the difference in level between the surface of the photodiode
62
and the lightproof film
65
in the opening, is almost entirely dependent on the thickness of the lightproof film
65
. Since the lightproof film
65
is extremely thin, the difference in level between the surface of the photodiode
62
and the lightproof film
65
, which defines the opening, is extremely small. This makes it possible to correct photosensitivity using the scaling method described above. In
FIG. 6
, the numeral
61
represents a semiconductor substrate,
64
represents an interlayer insulating film,
66
and
67
represents flattening insulating films, and
68
represents a microlens.
By contrast, in an amplifier-type solid-state image sensor device known as a CMOS sensor, the difference in level between the surface of the photodiode
72
and the metal film (aluminum wire, or aluminum lightproof film, or the like)
74
, which defines the opening, is generally more than 1 &mgr;m, as shown in FIG.
7
. As a result, even when the conventional technique of scaling is carried out using the microlens
76
of the color filter portion, the metal film
74
, which defines the opening of the photodiode
72
, cuts off the injected light, reducing the amount of light injected to the photodiode
72
at the peripheral portion of the semiconductor chip. Therefore, sensitivity cannot be adequately corrected by scaling with the microlens
76
. Thus conventional CMOS sensors have a disadvantage that sensitivity cannot be adequately corrected, due to the fact that the difference in level between the surface of the photodiode and the metal film which defines the opening, is more than 1 &mgr;m, thereby making it impossible to match the amount of light injected at the center of the semiconductor chip to the amount injected at the peripheral portion of the semiconductor chip, even by scaling with the microlens. In
FIG. 7
, numerals
73
and
74
represent insulating films for flattening,
77
represents an object lens, and
78
represents the light path.
BRIEF SUMMARY OF THE INVENTION
The present invention has been devised to solve the problems described above, and aims to provide an amplifier-type solid-state image sensor device wherein the amounts of light injected to the center and peripheral portion of the image sensing region can be matched even when there is a considerable difference in level between the surface of the photodiode and the metal film which defines the opening, thereby obtaining closely similar levels of photosensitivity at the center and peripheral portion of the image sensing region.
In order to solve the problems described above, an amplifier-type solid-state image sensor device according to a first aspect of the present invention comprises a plurality of unit cells, each comprising a photoconverter and a signal scanning circuit, arranged two-dimensionally in an image sensing region on a semiconductor substrate; signal lines provided on the semiconductor substrate, for reading out signals from the cells in the image sensing region; and a metal film having openings defining regions of the photoconverters of the unit cells, onto which regions light is radiated through the openings, a center position of each of the openings of the metal film being displaced to the side of the center of the image sensing region with respect to a center position of the photoconverter of a corresponding unit cell.
In the amplifier-type solid-state image sensor device according to the first aspect of the present invention, the amplifier-type solid-state image sensor device may further comprise microlenses arranged for the unit cells, a center position of each of the microlenses being displaced to the side of the center of the image sensing region with respect to a center position of the photoconverter of a corresponding unit cell.
In the amplifier-type solid-state image sensor device according to the first aspect of the present invention, the metal film may comprise a aluminum wire film.
In the amplifier-type solid-state image sensor device according to the first aspect of the present invention, the metal film may comprise a film made of a refractory metal.
In the amplifier-type solid-state image sensor device according to the first aspect of the present invention, the refractory metal may include titanium, tungsten, and molybdenum.
In the amplifier-type solid-state image sensor device according to the first aspect of the present invention, the metal film may comprise a film made of a metal compound.
In the amplifier-type solid-state image sensor device according to the first aspect of the present invention, the metal film may comprise a aluminum lightproof film.
An amplifier-type solid-state image sensor device according to a second aspect of the present invention comprises a plurality of unit cells, each comprising a photoconverter and a signal scanning circuit, arranged two-dimensionally in an image sensing region on a semiconductor substrate; signal lines provided on the semiconductor substrate, for reading out signals from the cells in the image sensing region; and a metal film having openings defining regions of the photoconverters of the unit cells, onto which regions light is radiated through the openings, a center position of each of the openings of the metal film being displaced to the side of the center of the image sensing region with respect to a center position of the photoconverter of a corresponding unit cell, the areas of those of the openings of the metal film, which are in a peripheral portion of the image sensing region, being larger than the areas of those of the openings of the metal film, which are in a center portion of the image sensing region.
In the amplifier-type solid-state image sensor device according to the second aspect of the present invention, the amplifier-type solid-state image sensor device may further comprise microlenses arranged for the unit cells, a center position of each of the microlenses being displaced to the side of the center of the image sensing region with respect to a center position of the photoconverter of a corresponding unit cell.
In the amplifier-type solid-state image sensor device according to the second aspect of the present invention, the metal film may comprise a aluminum wire
Ihara Hisanori
Ishiwata Hiroaki
Mori Akiko
Yamaguchi Tetsuya
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Meier Stephen D.
Mitchell James
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