Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Charge transfer device
Reexamination Certificate
1999-12-22
2003-06-17
Munson, Gene M. (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Charge transfer device
C257S233000, C257S249000, C257S413000
Reexamination Certificate
active
06580105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid-state imaging device and a method for manufacturing a solid-state imaging device, and more particularly it relates to a solid-state imaging device in which a single-layer electrically conductive electrode film is processed so as to form a charge transfer electrode, wherein a narrow interelectrode gap is flattened, with improved step coverage in a metal interconnect or metal light-shielding film formed thereon.
2. Background of the Invention
FIG.
8
and
FIG. 9
of the accompanying drawings show a sequence of cross-section views illustrating the processes in manufacturing a solid-state imaging device that uses a conventional buried type photodiode as an photoelectric conversion section (refer to Japanese Unexamined Patent Publication (KOKAI) No.5-267638).
In the above-noted process, thermal diffusion is first used to form a first p-type well layer
502
and a second p-type well
503
onto an n-type semiconductor substrate
501
, after which ion implantation of phosphorus is done to form a vertical charge transfer section
504
. Boron is then ion implanted to form a channel stopping region
506
and a charge reading region
505
(FIG.
8
(
a
)).
Next, the surface of the n-type semiconductor substrate is thermally oxidized to form a gate electrode film
507
, after which, as shown in FIG.
8
(
b
), low-pressure CVD is used to form a charge transfer electrode material film
508
on the gate electrode
507
. Patterning is then done for forming the reading electrode.
Then, photoresist
509
is used as a mask in performing dry etching so as to form a charge transfer electrode
510
. Next, the charge transfer electrode with the photoresist remaining is used as a mask in performing self-aligning ion implantation of phosphor, so as to form the n-type well
511
that will serve as the photodiode. When this is done, the film thickness of the photoresist
509
is made approximately 3 &mgr;m, so that the phosphorus ions do not penetrate (FIG.
8
(
c)).
Then, to form the buried type photodiode, the photoresist
509
is removed, after which boron is ion implanted with the charge transfer electrode
510
used as a mask, thereby forming a p+ type region
512
.
While FIG.
8
and
FIG. 9
show a cross-section view of a pixel in the processes of manufacturing a solid-state imaging device, the plan view of pattern arrangement is, for example, as shown in FIG.
10
.
In
FIG. 10
, a the charge transfer electrode is made by processing a single-layer charge transfer electrode material, a photoelectric conversion section being formed as a region enclosed within the charge transfer electrode. The cross-section views of FIG.
8
and
FIG. 9
are as seen along the cutting line A-A′ in FIG.
10
.
Four charge transfer electrodes taken as a unit, with a pulses of different phases ((&PHgr;
1
to &PHgr;
4
) applied to each, and in order to perform charge transfer using these pulses, it is necessary to provide a region
614
that separates the charge transfer electrodes in the row direction.
FIG. 11
is a cross-section view along the cutting line B-B′ shown in
FIG. 10. A
region
714
is formed which separates the charge transfer electrodes in the row direction, a metal light-shielding film
717
being formed thereon, with an intervening interlayer insulation film
716
therebetween, thereby preventing light from striking the vertical charge transfer section.
In the above-noted solid-state imaging device of the past, however, as shown in
FIG. 12
, because the region (interelectrode gap) that separates the charge transfer electrodes in the row direction is formed with a short distance of approximately 0.25 &mgr;m to 0.50 &mgr;m, porosity develops in the interlayer insulation film
816
formed thereover or locations of poor coverage occur, so that breaks
820
occur in the metal light-shielding film or metal interconnect formed thereover, thereby causing the problem of deterioration in either the light-blocking characteristics or the charge transfer characteristics.
One method that can be envisioned to prevent interconnect breakage is that of flattening the entire surface before providing the interconnects. When this is done, however, because the photoelectric conversion section as shown in
FIG. 13
is also flattened, there is an increase in the height of the metal light-shielding film from the surface of the substrate, so that angularly incident light
921
enters the charge transfer region, leading to a deterioration in smear characteristics.
Accordingly, it is an object of the present invention to solve the above-noted problem in a convetional solid-state imaging device, by providing a solid-state imaging device wherein a charge transfer electrode is formed by etching a single-layer charge-transfer material film, this etching region being divided into a first region to be divided in the row direction and a second region on a photoelectric conversion section, the etching region of the first region being filled with an insulation film, so as to flatten only the top part of the vertical charge transfer section or the bottom part of a region formed of a metal wiring for applying a drive voltage to a charge transfer electrode, thereby achieving a solid-state imaging device with good formation of metal wirings, without a deterioration of the smear characteristics.
SUMMARY OF THE INVENTION
In order to achieve the above-noted object, the present invention has the following basic technical constitution.
Specifically, the first aspect of the present invention is a solid-state imaging device comprising: a photoelectric conversion section formed within a surface region of semiconductor layer of a first conductivity type; a charge transfer section of a second conductivity type formed adjacent to the photoelectric conversion section within the surface region of the semiconductor layer of the first conductivity type, which receives and transfers a signal charge generated by the photoelectric conversion section; a read-out section formed in the surface region of the semiconductor layer of the first conductivity type for reading the signal generated by said photoelectric conversion section to the charge transfer section; and a single-layer charge transfer electrode formed over the read-out section and the charge transfer section, with an intervening gate insulation film therebetween, a region that separates the charge transfer electrode is filled with an insulation film having a height that is equivalent to or less than that of the charge transfer electrode.
In the second aspect of the present invention, a silicide film is formed on the surface of the charge transfer electrode.
The first aspect of a method of the present invention is a method for manufacturing a solid-state imaging device, the solid-state imaging device comprising: a photoelectric conversion section formed within a surface region of semiconductor layer of a first conductivity type; a charge transfer section of a second conductivity type formed adjacent to the photoelectric conversion section within the surface region of the semiconductor layer of the first conductivity type, which receives and transfers a signal charge generated by the photoelectric conversion section; a read-out section formed in the surface region of the semiconductor layer of the first conductivity type for reading the signal generated by the photoelectric conversion section to the charge transfer section; and a single-layer charge transfer electrode formed over the read-out section and the charge transfer section, with an intervening gate insulation film therebetween, an insulation film separating mutually adjacent the charge transfer electrodes; and a light-shielding film provided on the insulation film, the method comprising: a first step of etching of a first region on an electrically conductive electrode material film on the gate insulation film so as to divide the electrically conductive electrode material film and form the charge transfer electrodes; a second step of
Hatano Keisuke
Horiba Shinichi
Dickstein , Shapiro, Morin & Oshinsky, LLP
Munson Gene M.
NEC Electronic Corporation
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